Severe steatosis increases hepatocellular injury and impairs liver regeneration in a rat model of partial hepatectomy

An anatomical analysis of liver volume and quality by ethnicity in a New Zealand population

BACKGROUND

Post-hepatectomy liver failure is a major cause of mortality, where future liver remnant (FLR) is the key controllable factor. Recommended minimum FLR is influenced by quality of liver parenchyma. Historical research has often failed to include Māori and Pacific Island (PI) populations despite worse health outcomes. Liver analysis by ethnicity is one such example of this. The aims were to determine digital FLR for various anatomical hepatectomies, investigate any correlations between computed tomography (CT) hepatic textural analysis and body mass index (BMI); and assess the variance of these relationships for different ethnicities.

METHOD

One hundred and fifty-one patients who underwent abdominal CT scans at Burwood Hospital, Christchurch were retrospectively analysed. Māori and PI patients were selectively recruited to represent New Zealand's diversity. Liver volumetry, segmental ratio, and intra-hepatic fat deposits (IHFD) per ethnicity were examined.

RESULTS

Median age of the cohort was 66 (19-95) and 75 (50%) were males. 68%, 23% and 9% patients identified as being European, Māori/PI and Asian, respectively. No statistically significant difference in volume or segment/total volume ratio were noted across different ethnicities. Obese patients had higher IHFD compared with overweight and normal BMI groups. When stratified across ethnic groups, higher IHFD were observed in Asian compared with Māori/PI populations, despite lower BMI.

CONCLUSION

No significant variances in liver volumetry were found across different ethnic groups in New Zealand. However association between BMI and IHFD varied across different ethnic cohorts. Consequently, knowledge of liver volumetry is not enough; patient liver quality and ethnicity should considered for hepatic-surgery planning.

Multiscale 3D genome organization underlies duck fatty liver with no adipose inflammation or serious injury

Non-alcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease. Little is known about how gene expression and chromatin structure are regulated in NAFLD due to lack of suitable model. Ducks naturally develop fatty liver similar to serious human non-alcoholic fatty liver (NAFL) without adipose inflammation and liver fibrosis, thus serves as a good model for investigating molecular mechanisms of adipose metabolism and anti-inflammation. Here, we constructed a NAFLD model without adipose inflammation and liver fibrosis in ducks. By performing dynamic pathological and transcriptomic analyses, we identified critical genes involving in regulation of the NF-κB and MHCII signaling, which usually lead to adipose inflammation and liver fibrosis. We further generated dynamic three-dimensional chromatin maps during liver fatty formation and recovery. This showed that ducks enlarged hepatocyte cell nuclei to reduce inter-chromosomal interaction, decompress chromatin structure, and alter strength of intra-TAD and loop interactions during fatty liver formation. These changes partially contributed to the tight control the NF-κB and the MHCII signaling. Our analysis uncovers duck chromatin reorganization might be advantageous to maintain liver regenerative capacity and reduce adipose inflammation. These findings shed light on new strategies for NAFLD control.

HMGB2 Promotes De Novo Lipogenesis to Accelerate Hepatocyte Proliferation During Liver Regeneration

Liver regeneration is a well-orchestrated compensatory process that is regulated by multiple factors. We recently reported the importance of the chromatin protein, a high-mobility group box 2 (HMGB2) in mouse liver regeneration. However, the molecular mechanism remains unclear. In this study, we aimed to study how HMGB2 regulates hepatocyte proliferation during liver regeneration. Seventy-percent partial hepatectomy (PHx) was performed in wild-type (WT) and HMGB2-knockout (KO) mice, and the liver tissues were used for microarray, immunohistochemistry, quantitative polymerase chain reaction (qPCR), and Western blotting analyses. In the WT mice, HMGB2-positive hepatocytes colocalized with cell proliferation markers. In the HMGB2-KO mice, hepatocyte proliferation was significantly decreased. Oil Red O staining revealed the transient accumulation of lipid droplets at 12-24 hr after PHx in the WT mouse livers. In contrast, decreased amount of lipid droplets were found in HMGB2-KO mouse livers, and it was preserved until 36 hr. The microarray, immunohistochemistry, and qPCR results demonstrated that the expression of lipid metabolism-related genes was significantly decreased in the HMGB2-KO mouse livers. The in vitro experiments demonstrated that a decrease in the amount of lipid droplets correlated with decreased cell proliferation activity in HMGB2-knockdown cells. HMGB2 promotes de novo lipogenesis to accelerate hepatocyte proliferation during liver regeneration.

On a deterministic mathematical model which efficiently predicts the protective effect of a plant extract mixture in cirrhotic rats

In this work, we propose a mathematical model that describes liver evolution and concentrations of alanine aminotransferase and aspartate aminotransferase in a group of rats damaged with carbon tetrachloride. Carbon tetrachloride was employed to induce cirrhosis. A second groups damaged with carbon tetrachloride was exposed simultaneously a plant extract as hepatoprotective agent. The model reproduces the data obtained in the experiment reported in [Rev. Cub. Plant. Med. 22(1), 2017], and predicts that using the plants extract helps to get a better natural recovery after the treatment. Computer simulations show that the extract reduces the damage velocity but does not avoid it entirely. The present paper is the first report in the literature in which a mathematical model reliably predicts the protective effect of a plant extract mixture in rats with cirrhosis disease. The results reported in this manuscript could be used in the future to help in fighting cirrhotic conditions in humans, though more experimental and mathematical work is required in that case.

High-fat diet increases mortality and intensifies immunometabolic changes in septic mice

Immunometabolic changes in the liver and white adipose tissue (WAT) caused by high-fat (HF) diet intake may worse metabolic adaptation and protection against pathogens in sepsis. We investigate the effect of chronic HF diet (15 weeks) on mortality and immunometabolic responses in female mice after sepsis induced by cecum ligation and perforation (CLP). At week 14, animals were divided into four groups: sham C diet (C-Sh), sepsis C diet (C-Sp), sham HF diet (HF-Sh) and sepsis HF diet (HF-Sp). The surviving animals were euthanised on the 7th day. The HF diet decreased survival rate (58.3% vs 76.2% C-Sp group), increased serum cytokine storm (IL-6 (1.41 ×; vs HF-Sh), IL-1β (1.37 ×; vs C-Sp), TNF (1.34 ×; vs C-Sp and 1.72 ×; vs HF-Sh), IL-17 (1.44 ×; vs HF-Sh), IL-10 (1.55 ×; vs C-Sp and 1.41 ×; HF-Sh), WAT inflammation (IL-6 (8.7 ×; vs C-Sp and 2.4 ×; vs HF-Sh), TNF (5 ×; vs C-Sp and 1.7 ×;vs HF-Sh), IL-17 (1.7 ×; vs C-Sp), IL-10 (7.4 ×; vs C-Sp and 1.3 ×; vs HF-Sh), and modulated lipid metabolism in septic mice. In the HF-Sp group liver's, we observed hepatomegaly, hydropic degeneration, necrosis, an increase in oxidative stress (reduction of CAT activity (-81.7%; vs HF-Sh); increase MDA levels (82.8%; vs HF-Sh), and hepatic IL-6 (1.9 ×; vs HF-Sh), and TNF (1.3 × %;vs HF-Sh) production. Furthermore, we found a decrease in the total number of inflammatory, mononuclear cells, and in the regenerative processes, and binucleated hepatocytes in a HF-Sp group liver's. Our results suggested that the organism under metabolic stress of a HF diet during sepsis may worsen the inflammatory landscape and hepatocellular injury and may harm the liver regenerative process.

Impact of neoadjuvant chemotherapy on post-hepatectomy regeneration for patients with colorectal cancer liver metastasis - Systematic review and meta-analysis

BACKGROUND

Today, there is still debate on the impact of neoadjuvant chemotherapy (NeoChem) on liver regeneration (LivReg). The objectives of this study were to assess the impact of NeoChem and its characteristics (addition of bevacizumab, number of cycles and time from end of NeoChem) on post-hepatectomy LivReg.

MATERIAL & METHODS

Studies reporting LivReg in patients submitted to liver resection were included. Pubmed, Scopus, Web of Science, Embase, and Cochrane databases were searched. Only studies comparing NeoChem vs no chemotherapy or comparing chemotherapy characteristics from 1990 to present were included. Two researchers individually screened the identified records registered in a predesigned database. Primary outcome was future liver remnant regeneration rate (FLR3). Bias of the studies was evaluated with the ROBINS-I tool, and quality of evidence with the GRADE system. Data was presented as mean difference or standard mean difference.

RESULTS

Eight studies with a total of 681 patients were selected. Seven were retrospective and one prospective comparative cohort studies. In patients submitted to major hepatectomy, NeoChem did not have an impact on LivReg (MD 3.12, 95% CI -2,12-8.36, p 0,24). Adding bevacizumab to standard NeoChem was associated with better FLR3 (SMD 0.45, 95% CI 0.19-0.71, p 0.0006).

DISCUSSION

The main drawback of this review is the retrospective nature of the available studies. NeoChem does not have a negative impact on postoperative LivReg in patients submitted to liver resection. Regimens with bevacizumab seem to be associated with better postoperative LivReg rates when compared to standard NeoChem.

Administration of Secretome Derived from Human Mesenchymal Stem Cells Induces Hepatoprotective Effects in Models of Idiosyncratic Drug-Induced Liver Injury Caused by Amiodarone or Tamoxifen

Drug-induced liver injury (DILI) is one of the leading causes of acute liver injury. While many factors may contribute to the susceptibility to DILI, obese patients with hepatic steatosis are particularly prone to suffer DILI. The secretome derived from mesenchymal stem cell has been shown to have hepatoprotective effects in diverse in vitro and in vivo models. In this study, we evaluate whether MSC secretome could improve DILI mediated by amiodarone (AMI) or tamoxifen (TMX). Hepatic HepG2 and HepaRG cells were incubated with AMI or TMX, alone or with the secretome of MSCs obtained from human adipose tissue. These studies demonstrate that coincubation of AMI or TMX with MSC secretome increases cell viability, prevents the activation of apoptosis pathways, and stimulates the expression of priming phase genes, leading to higher proliferation rates. As proof of concept, in a C57BL/6 mouse model of hepatic steatosis and chronic exposure to AMI, the MSC secretome was administered endovenously. In this study, liver injury was significantly attenuated, with a decrease in cell infiltration and stimulation of the regenerative response. The present results indicate that MSC secretome administration has the potential to be an adjunctive cell-free therapy to prevent liver failure derived from DILI caused by TMX or AMI.

Is liver regeneration key in hepatocellular carcinoma development?

The liver is the largest organ of the mammalian body and has the remarkable ability to fully regenerate in order to maintain tissue homeostasis. The adult liver consists of hexagonal lobules, each with a central vein surrounded by six portal triads localized in the lobule border containing distinct parenchymal and nonparenchymal cells. Because the liver is continuously exposed to diverse stress signals, several sophisticated regenerative processes exist to restore its functional status following impairment. However, these stress signals can affect the liver's capacity to regenerate and may lead to the development of hepatocellular carcinoma (HCC), one of the most aggressive liver cancers. Here, we review the mechanisms of hepatic regeneration and their potential to influence HCC development.

The transcription factor ATF3 switches cell death from apoptosis to necroptosis in hepatic steatosis in male mice

Hepatocellular death increases with hepatic steatosis aggravation, although its regulation remains unclear. Here we show that hepatic steatosis aggravation shifts the hepatocellular death mode from apoptosis to necroptosis, causing increased hepatocellular death. Our results reveal that the transcription factor ATF3 acts as a master regulator in this shift by inducing expression of RIPK3, a regulator of necroptosis. In severe hepatic steatosis, after partial hepatectomy, hepatic ATF3-deficient or -overexpressing mice display decreased or increased RIPK3 expression and necroptosis, respectively. In cultured hepatocytes, ATF3 changes TNFα-dependent cell death mode from apoptosis to necroptosis, as revealed by live-cell imaging. In non-alcoholic steatohepatitis (NASH) mice, hepatic ATF3 deficiency suppresses RIPK3 expression and hepatocellular death. In human NASH, hepatocellular damage is correlated with the frequency of hepatocytes expressing ATF3 or RIPK3, which overlap frequently. ATF3-dependent RIPK3 induction, causing a modal shift of hepatocellular death, can be a therapeutic target for steatosis-induced liver damage, including NASH.

Impact of hepatic steatosis on treatment response of autoimmune hepatitis: A retrospective multicentre analysis

Background

There is a paucity of data on whether steatosis impacts autoimmune hepatitis (AIH) treatment response. We aimed to evaluate the influence of baseline steatosis on the biochemical response, fibrosis progression, and adverse longterm outcomes of AIH.

Methods

Steatosis was diagnosed by a controlled attenuation parameter (CAP) ≥ 248 dB / m. Only patients who underwent immunosuppressive therapy with available liver histological material at diagnosis and qualified CAP within seven days of the liver biopsy were included. Univariate and multivariate analyses were subsequently conducted.

Results

The multicentre and retrospective cohort enrolled 222 subjects (88.3% female, median age 54 years, median follow-up 48 months) in the final analysis, and 56 (25.2%) patients had hepatic steatosis. Diabetes, hypertension, and significant fibrosis at baseline were more common in the steatosis group than in the no steatosis group. After adjusting for confounding factors, hepatic steatosis was an independent predictor of insufficient biochemical response (OR: 8.07) and identified as an independent predictor of long-term adverse outcomes (HR: 4.07). By subgroup multivariate analysis (different degrees of steatosis, fibrosis, and prednisone dose), hepatic steatosis independently showed a relatively stable correlation with treatment response. Furthermore, in contrast to those without steatosis, a significant increase in liver stiffness (LS) was observed in patients with steatosis (4.1%/year vs. -16%/year, P < 0.001).

Conclusions

Concomitant hepatic steatosis was significantly associated with poor response to treatment in AIH patients. Routine CAP measurements are therefore essential to guide the management of AIH.

The obesity and nonalcoholic fatty liver disease mouse model revisited: Liver oxidative stress, hepatocyte apoptosis, and proliferation

The study revisited the diet-induced obesity (DIO) mice and the nonalcoholic fatty liver disease (NAFLD) pathogenesis to serve as a translational model. Hepatic beta-oxidation pathways, lipogenesis, oxidative stress, hepatocyte apoptosis, and proliferation were investigated in obese mice. Three-month-old male mice were divided according to their diet for fifteen weeks, the control diet (C group, containing 10% energy from fat) and the high-fat diet (HF group, containing 50% energy from fat). Body weight (BW), liver mass, and steatosis were higher in the HF group than in the C group. Also, gene expression related to beta-oxidation and lipogenesis showed an adverse profile, and insulin and glucose signaling pathways were impaired in the HF group compared to the C group. As a result, steatosis was prevalent in the HF group but not in the C group. Furthermore, the pathways that generate NAFLD were negatively modulated by oxidative stress in the HF animals than in the C ones. The caspase 3 immunolabeled HF hepatocytes with increased gene and protein expressions related to apoptosis while proliferating cell nuclear antigen labeled C hepatocytes. In conclusion, the findings in the DIO mouse model reproduce the NAFLD profile relative to the human NAFLD's apoptosis, insulin signaling, lipogenesis, beta-oxidation, and oxidative stress. Therefore, the model is adequate for a translational perspective's morphological, biochemical, and molecular research on NAFLD.

Hypersampones A-C, Three Nor-Polycyclic Polyprenylated Acylphloroglucinols with Lipid-Lowering Activity from Hypericum sampsonii

Hypersampones A-C (1-3), three unprecedented nor-polycyclic polyprenylated acylphloroglucinols (PPAPs), were isolated from Hypericum sampsonii. These compounds represent the first nor-PPAPs with an unexpected tetracyclic 6/5/5/6 ring system. Their structures were assigned through the analysis of detailed spectroscopic data, X-ray crystallography, and electronic circular dichroism calculations. Compound 1 significantly inhibited the accumulation of lipid in an oleic acid-treated HepG2 cell model by suppressing the protein expression of FAS and ACACA at 5 μM.

Crosstalk of hepatocyte nuclear factor 4a and glucocorticoid receptor in the regulation of lipid metabolism in mice fed a high-fat-high-sugar diet

Background

Hepatocyte nuclear factor 4α (HNF4α) and glucocorticoid receptor (GR), master regulators of liver metabolism, are down-regulated in fatty liver diseases. The present study aimed to elucidate the role of down-regulation of HNF4α and GR in fatty liver and hyperlipidemia.

Methods

Adult mice with liver-specific heterozygote (HET) and knockout (KO) of HNF4α or GR were fed a high-fat-high-sugar diet (HFHS) for 15 days. Alterations in hepatic and circulating lipids were determined with analytical kits, and changes in hepatic mRNA and protein expression in these mice were quantified by real-time PCR and Western blotting. Serum and hepatic levels of bile acids were quantified by LC-MS/MS. The roles of HNF4α and GR in regulating hepatic gene expression were determined using luciferase reporter assays.

Results

Compared to HFHS-fed wildtype mice, HNF4α HET mice had down-regulation of lipid catabolic genes, induction of lipogenic genes, and increased hepatic and blood levels of lipids, whereas HNF4α KO mice had fatty liver but mild hypolipidemia, down-regulation of lipid-efflux genes, and induction of genes for uptake, synthesis, and storage of lipids. Serum levels of chenodeoxycholic acid and deoxycholic acid tended to be decreased in the HNF4α HET mice but dramatically increased in the HNF4α KO mice, which was associated with marked down-regulation of cytochrome P450 7a1, the rate-limiting enzyme for bile acid synthesis. Hepatic mRNA and protein expression of sterol-regulatory-element-binding protein-1 (SREBP-1), a master lipogenic regulator, was induced in HFHS-fed HNF4α HET mice. In reporter assays, HNF4α cooperated with the corepressor small heterodimer partner to potently inhibit the transactivation of mouse and human SREBP-1C promoter by liver X receptor. Hepatic nuclear GR proteins tended to be decreased in the HNF4α KO mice. HFHS-fed mice with liver-specific KO of GR had increased hepatic lipids and induction of SREBP-1C and PPARγ, which was associated with a marked decrease in hepatic levels of HNF4α proteins in these mice. In reporter assays, GR and HNF4α synergistically/additively induced lipid catabolic genes.

Conclusions

induction of lipid catabolic genes and suppression of lipogenic genes by HNF4α and GR may mediate the early resistance to HFHS-induced fatty liver and hyperlipidemia.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-022-01654-6.

Fibrosis and hepatic regeneration mechanism

Liver cirrhosis is the final stage of continuous hepatic inflammatory activity derived by viral, metabolic or autoimmune origin. In the last years, cirrhosis was considered a unique and static condition; recently was accepted some patients subgroups with different liver injury degrees that coexist under the same diagnosis, with implications about the natural disease history. The liver growth factor (LGF) is a potent in vivo and in vitro mitogenic agent and an inducer of hepatic regeneration (HR) through the hepatocytes DNA synthesis. The clinical implications of the LGF levels in cirrhosis, are not clear and even with having a fundamental role in the liver regeneration processes, the studies suggest that it could be a cirrhosis severity marker, in acute liver failure and in chronic hepatitis. Its role as predictor of mortality in fulminant hepatic insufficiency patients has been suggested. HR is one of the most enigmatic and fascinating biological phenomena. The rapid volume and liver function restoration after a major hepatectomy (>70%) or severe hepatocellular damage and its strict regulation of tissue damage response after the cessation, is an exclusive property of the liver. HR is the clinical applications fundament, such as extensive hepatic resections (>70% of the liver parenchyma), segmental transplantation or living donor transplantation, sequential hepatectomies, isolated portal embolization or associated with in situ hepatic transection, temporary artificial support in acute liver failure and the possible cell therapy clinical applications.

Liver regeneration biology: Implications for liver tumour therapies

The liver has remarkable regenerative potential, with the capacity to regenerate after 75% hepatectomy in humans and up to 90% hepatectomy in some rodent models, enabling it to meet the challenge of diverse injury types, including physical trauma, infection, inflammatory processes, direct toxicity, and immunological insults. Current understanding of liver regeneration is based largely on animal research, historically in large animals, and more recently in rodents and zebrafish, which provide powerful genetic manipulation experimental tools. Whilst immensely valuable, these models have limitations in extrapolation to the human situation. In vitro models have evolved from 2-dimensional culture to complex 3 dimensional organoids, but also have shortcomings in replicating the complex hepatic micro-anatomical and physiological milieu. The process of liver regeneration is only partially understood and characterized by layers of complexity. Liver regeneration is triggered and controlled by a multitude of mitogens acting in autocrine, paracrine, and endocrine ways, with much redundancy and cross-talk between biochemical pathways. The regenerative response is variable, involving both hypertrophy and true proliferative hyperplasia, which is itself variable, including both cellular phenotypic fidelity and cellular trans-differentiation, according to the type of injury. Complex interactions occur between parenchymal and non-parenchymal cells, and regeneration is affected by the status of the liver parenchyma, with differences between healthy and diseased liver. Finally, the process of termination of liver regeneration is even less well understood than its triggers. The complexity of liver regeneration biology combined with limited understanding has restricted specific clinical interventions to enhance liver regeneration. Moreover, manipulating the fundamental biochemical pathways involved would require cautious assessment, for fear of unintended consequences. Nevertheless, current knowledge provides guiding principles for strategies to optimise liver regeneration potential.

Maternal high-fat diet consumption programs male offspring to mitigate complications in liver regeneration

In the last decades, obesity and nonalcoholic fatty liver disease (NAFLD) have become increasingly prevalent in wide world. Fatty liver can be detrimental to liver regeneration (LR) and offspring of obese dams (HFD-O) are susceptible to NAFLD development. Here we evaluated LR capacity in HFD-O after partial hepatectomy (PHx). HFD-O re-exposed or not to HFD in later life were evaluated for metabolic parameters, inflammation, proliferation, tissue repair markers and survival rate after PHx. Increasing adiposity and fatty liver were observed in HFD-O. Despite lower IL-6 levels, Ki67 labeling, cells in S phase and Ciclin D1/PCNA protein content, a lower impact on survival rate was found after PHx, even when re-exposed to HFD. However, no difference was observed between offspring of control dams (SC-O) and HFD-O after surgery. Although LR impairment is dependent of steatosis development, offspring of obese dams are programmed to be protected from the damage promoted by HFD.

Verapamil induces autophagy to improve liver regeneration in non-alcoholic fatty liver mice

Verapamil can restore intracellular calcium homeostasis, increase the fusion of autophagosomes and lysosomes, reduce lipid droplet accumulation and inhibit inflammation and insulin resistance in high-fat-fed mice. The present study aimed to investigate verapamil's effect and its underlying liver regeneration mechanism in mice with non-alcoholic fatty liver. After 50% hepatectomy was performed, the changes of autophagy and liver regeneration were evaluated by detecting cell proliferation and autophagy at each time point. Then, 25mg/kg verapamil was injected intraperitoneally for 10 d before an operation in the mild to moderate fatty liver and severe fatty liver groups. The control group and mild to moderate fatty liver group reached the peak of proliferation at 24-48h after operation, and the mice with severe fatty liver and steatohepatitis reached the peak at 48-72h. Autophagy in the normal group and mild to moderate fatty liver group reached the peak 48 hours after operation. Verapamil injection can enhance autophagy, reduce the weight of fatty liver mice, improve liver function and liver regeneration. Verapamil can induce autophagy, improve hepatocyte function and promote hepatocyte regeneration through the mTOR independent signaling pathway, thus improving the process of liver regeneration after partial hepatectomy.

Impact of Metabolic Syndrome on Postoperative Outcomes Among Medicare Beneficiaries Undergoing Hepatectomy

INTRODUCTION

The impact of metabolic syndrome (MetS) on postoperative outcomes following liver surgery is not well studied. The objective of the current study was to examine the association of MetS with individual perioperative outcomes, as well as the composite "textbook outcome" (TO) following liver resection for both benign and malignant indications.

METHODS

The Medicare 100% Standard Analytic Files were reviewed to identify Medicare beneficiaries who underwent hepatectomy between 2013 and 2017. The impact of MetS on complications, length of stay (LOS), 90-day readmission, 90-day mortality, and TO following hepatectomy was investigated.

RESULTS

Among 13,898 patients who underwent hepatectomy, 2491 (17.9%) had MetS while 11,407 (82.1%) did not. Patients with MetS were more often male (59.1% vs 48.5%), Black (8.5% vs 6.6%), and had a diagnosis of cancer (69.9% vs 65.1%) (all p<0.001). On multivariable analysis, patients with MetS had higher odds of complications (OR 1.41, 95% CI 1.28-1.55), 90-day readmission (OR 1.27, 95% CI 1.15-1.40), and 90-day mortality (OR 1.32, 95% CI 1.13-1.54). In turn, patients with MetS had markedly lower odds of TO following hepatectomy compared with non-MetS patients (OR=0.76, 95% CI 0.70-0.83). Of note, patients with MetS had lower odds of TO after both minimally invasive (OR=0.59, 95% CI 0.43-0.81) and open (OR=0.75, 95% CI 0.68-0.82) liver surgery. Individuals with MetS also had a higher overall expenditure during the index hospitalization compared with non-MetS patients ($19.9k USD vs. $18.8k USD, p<0.001).

CONCLUSION

Patients with MetS had increased morbidity and mortality, as well as lower likelihood to achieve a TO following liver resection. MetS increased the operative risk and overall Medicare expenditures associated with hepatic resection.

Clinical Practice Guidelines for Liver Transplantation in Saudi Arabia

The demand for liver transplantation in the Kingdom of Saudi Arabia (KSA) is associated with the country's high burden of liver disease. Trends in the epidemiology of liver transplantation indications among recipients in KSA have changed over 20 years. Non-alcoholic steatohepatitis has eclipsed the hepatitis C virus in the country due to the effective treatment strategies for HCV. Risk factors for NASH, like type 2 diabetes mellitus, obesity, and hyperlipidemia, are becoming a major concern and a leading indication for liver transplantation in the KSA. There is also a significantly increased prevalence and incidence of genetic adult familial liver diseases in KSA. New immunosuppressive agents and preservation solutions, improved surgical capabilities, and early disease recognition and management have increased the success rate of liver transplant outcome but concerns about the side effects of immunosuppressive therapy can jeopardise long-term survival outcomes. Despite this, indications for liver transplantation continue to increase, resulting in ongoing challenges to maximize the number of potential donors and reduce patient mortality rate while expecting to get transplanted. The Saudi Center of Organ Transplant is the recognized National Organ Donation Agency for transplantation, which renders important support for procurement and allocation of organs. This guidance document aims to help healthcare providers in managing patients in the liver transplant setting.

Safe use of right lobe living donor livers with moderate steatosis in adult-to-adult living donor liver transplantation: a retrospective study

Hepatic steatosis (HS) beyond a certain degree can jeopardize living donor (LD) safety, particularly in right lobe (RL) donors, making it a major obstacle for donor pool expansion in adult-to-adult living donor liver transplantation (ALDLT). From July 2004 to June 2016, 58 LDs donated their RLs despite having moderate HS (30%-50% steatosis) determined by intraoperative biopsy at a single center. We performed greedy matching to compare the outcomes of the donors and recipients of this group with those of LDs with no HS. The mean left lobe (LL) HS value in the 58 cases was 20.9 ± 12.4%, which was significantly lower than the mean RL HS value (38.8 ± 6.7%, P < 0.001). The mean ratio of the remnant LL to the total liver volume was 37.8 ± 2.2. No differences were observed in the postoperative liver function and donor and recipient morbidity and mortality rates. The liver regeneration rates in recipients and donors at 1 month, 6 months, and 1 year postoperatively did not differ significantly. The patient and graft survival rates of the recipients showed no differences. The use of well-selected RL grafts with moderate steatosis does not impair graft function, recipient outcomes, or donor safety.

Pathophysiological Changes During Ischemia-reperfusion Injury in Rodent Hepatic Steatosis

BACKGROUND/AIM

Ischemia and reperfusion injuries may produce deleterious effects on hepatic tissue after liver surgery and transplantation. The impact of ischemia-reperfusion injury (IRI) on the liver depends on its substrate, the percentage of liver ischemic tissue subjected to IRI and the ischemia time. The consequences of IRI are more evident in pathologic liver substrates, such as steatotic livers. This review is the result of an extended bibliographic PubMed search focused on the last 20 years. It highlights basic differences encountered during IRI in lean and steatotic livers based on studies using rodent experimental models.

CONCLUSION

The main difference in cell death between lean and steatotic livers is the prevalence of apoptosis in the former and necrosis in the latter. There are also major changes in the effect of intracellular mediators, such as TNFα and IL-1β. Further experimental studies are needed in order to increase current knowledge of IRI effects and relevant mechanisms in both lean and steatotic livers, so that new preventive and therapeutic strategies maybe developed.

Monoacylglycerol Acyltransferase 1 Knockdown Exacerbates Hepatic Ischemia/Reperfusion Injury in Mice With Hepatic Steatosis

Nonalcoholic fatty liver disease (NAFLD) is becoming the most common indication for liver transplantation. The growing prevalence of NAFLD not only increases the demand for liver transplantation, but it also limits the supply of available organs because steatosis predisposes grafts to ischemia/reperfusion injury (IRI) and many steatotic grafts are discarded. We have shown that monoacylglycerol acyltransferase (MGAT) 1, an enzyme that converts monoacylglycerol to diacylglycerol, is highly induced in animal models and patients with NAFLD and is an important mediator in NAFLD-related insulin resistance. Herein, we sought to determine whether Mogat1 (the gene encoding MGAT1) knockdown in mice with hepatic steatosis would reduce liver injury and improve liver regeneration following experimental IRI. Antisense oligonucleotides (ASO) were used to knockdown the expression of Mogat1 in a mouse model of NAFLD. Mice then underwent surgery to induce IRI. We found that Mogat1 knockdown reduced hepatic triacylglycerol accumulation, but it unexpectedly exacerbated liver injury and mortality following experimental ischemia/reperfusion surgery in mice on a high-fat diet. The increased liver injury was associated with robust effects on the hepatic transcriptome following IRI including enhanced expression of proinflammatory cytokines and chemokines and suppression of enzymes involved in intermediary metabolism. These transcriptional changes were accompanied by increased signs of oxidative stress and an impaired regenerative response. We have shown that Mogat1 knockdown in a mouse model of NAFLD exacerbates IRI and inflammation and prolongs injury resolution, suggesting that Mogat1 may be necessary for liver regeneration following IRI and that targeting this metabolic enzyme will not be an effective treatment to reduce steatosis-associated graft dysfunction or failure.

Remodeling of whole-body lipid metabolism and a diabetic-like phenotype caused by loss of CDK1 and hepatocyte division

Cell cycle progression and lipid metabolism are well-coordinated processes required for proper cell proliferation. In liver diseases that arise from dysregulated lipid metabolism, hepatocyte proliferation is diminished. To study the outcome of CDK1 loss and blocked hepatocyte proliferation on lipid metabolism and the consequent impact on whole-body physiology, we performed lipidomics, metabolomics, and RNA-seq analyses on a mouse model. We observed reduced triacylglycerides in liver of young mice, caused by oxidative stress that activated FOXO1 to promote the expression of Pnpla2/ATGL. Additionally, we discovered that hepatocytes displayed malfunctioning β-oxidation, reflected by increased acylcarnitines (ACs) and reduced β-hydroxybutyrate. This led to elevated plasma free fatty acids (FFAs), which were transported to the adipose tissue for storage and triggered greater insulin secretion. Upon aging, chronic hyperinsulinemia resulted in insulin resistance and hepatic steatosis through activation of LXR. Here, we demonstrate that loss of hepatocyte proliferation is not only an outcome but also possibly a causative factor for liver pathology.

The effect of preoperative chemotherapy on liver regeneration after portal vein embolization/ligation or liver resection in patients with colorectal liver metastasis: a systematic review protocol

INTRODUCTION

Liver resection (LR) in patients with liver metastasis from colorectal cancer remains the only curative treatment. Perioperative chemotherapy improves prognosis of these patients. However, there are concerns regarding the effect of preoperative chemotherapy on liver regeneration, which is a key event in avoiding liver failure after LR. The primary objective of this systematic review is to assess the effect of neoadjuvant chemotherapy on liver regeneration after (LR) or portal vein embolization (PVE) in patients with liver metastasis from colorectal cancer. The secondary objectives are to evaluate the impact of the type of chemotherapy, number of cycles, and time between end of treatment and procedure (LR or PVE) and to investigate whether there is an association between degree of hypertrophy and postoperative liver failure.

METHODS

This meta-analysis will include studies reporting liver regeneration rates in patients submitted to LR or PVE. Pubmed, Scopus, Web of Science, Embase, and Cochrane databases will be searched. Only studies comparing neoadjuvant vs no chemotherapy, or comparing chemotherapy characteristics (bevacizumab administration, number of cycles, and time from finishing chemotherapy until intervention), will be included. We will select studies from 1990 to present. Two researchers will individually screen the identified records, according to a list of inclusion and exclusion criteria. Primary outcome will be future liver remnant regeneration rate. Bias of the studies will be evaluated with the ROBINS-I tool, and quality of evidence for all outcomes will be determined with the GRADE system. The data will be registered in a predesigned database. If selected studies are sufficiently homogeneous, we will perform a meta-analysis of reported results. In the event of a substantial heterogeneity, a qualitative systematic review will be performed.

DISCUSSION

The results of this systematic review may help to better identify the patients affected by liver metastasis that could present low regeneration rates after neoadjuvant chemotherapy. These patients are at risk to develop liver failure after extended hepatectomies and therefore are not good candidates for such aggressive procedures.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number: CRD42020178481 (July 5, 2020).

Loss of hepatocyte cell division leads to liver inflammation and fibrosis

The liver possesses a remarkable regenerative capacity based partly on the ability of hepatocytes to re-enter the cell cycle and divide to replace damaged cells. This capability is substantially reduced upon chronic damage, but it is not clear if this is a cause or consequence of liver disease. Here, we investigate whether blocking hepatocyte division using two different mouse models affects physiology as well as clinical liver manifestations like fibrosis and inflammation. We find that in P14 Cdk1Liv-/- mice, where the division of hepatocytes is abolished, polyploidy, DNA damage, and increased p53 signaling are prevalent. Cdk1Liv-/- mice display classical markers of liver damage two weeks after birth, including elevated ALT, ALP, and bilirubin levels, despite the lack of exogenous liver injury. Inflammation was further studied using cytokine arrays, unveiling elevated levels of CCL2, TIMP1, CXCL10, and IL1-Rn in Cdk1Liv-/- liver, which resulted in increased numbers of monocytes. Ablation of CDK2-dependent DNA re-replication and polyploidy in Cdk1Liv-/- mice reversed most of these phenotypes. Overall, our data indicate that blocking hepatocyte division induces biological processes driving the onset of the disease phenotype. It suggests that the decrease in hepatocyte division observed in liver disease may not only be a consequence of fibrosis and inflammation, but also a pathological cue.

CDK5RAP3 Deficiency Restrains Liver Regeneration after Partial Hepatectomy Triggering Endoplasmic Reticulum Stress

CDK5 regulatory subunit-associated protein 3 (CDK5RAP3) plays a crucial role in mammalian liver development and hepatic function by controlling hepatocyte proliferation and differentiation, glucose and lipid metabolism, UFMylation, and endoplasmic reticulum homeostasis. However, the role of CDK5RAP3 in liver regeneration remains unknown. A liver-specific Cdk5rap3 knockout (CKO) mouse model was used to study the function of CDK5RAP3 during liver regeneration induced by standard two-thirds partial hepatectomy (PHx). Twenty-four hours after PHx, the liver-to-body weight ratio was markedly higher in CKO mice than in wild-type mice. However, this ratio did not increase significantly and gradually over time after PHx in CKO mice. Hepatocyte proliferation was significantly delayed in CKO mice compared with wild-type mice. Meanwhile, CDK5RAP3 deficiency increased lipid accumulation, impaired glycogen synthesis, and lowered blood glucose levels after PHx. Critically, the absence of CDK5RAP3 seemed to promote an inflammatory response and induce apoptosis at a late stage of liver regeneration. In addition, CDK5RAP3 deficiency disrupted UFMylation homeostasis and aggravated endoplasmic reticulum stress in hepatocytes after PHx. Taken together, these data suggest that CDK5RAP3 enhances liver regeneration, at least partially via controlling cell cycle and glucose and lipid metabolism.

Remote Ischemic Preconditioning in a Cirrhotic Patient Undergoing Major Hepatectomy

Remote ischemic preconditioning (RIPC) has been shown to reduce ischemic reperfusion injury for patients undergoing hepatectomy for colorectal liver metastasis. We present a case of a 69-year-old male who underwent right hepatectomy for a multifocal hepatocellular carcinoma of the right liver and concomitant liver cirrhosis (Child-Pugh stage A). We performed portal vein embolization prior to surgery and intraoperative RIPC of the iliac vessels. The postoperative course after major hepatectomy went uneventful.

Cell cycle regulation in NAFLD: when imbalanced metabolism limits cell division

Cell division is essential for organismal growth and tissue homeostasis. It is exceptionally significant in tissues chronically exposed to intrinsic and external damage, like the liver. After decades of studying the regulation of cell cycle by extracellular signals, there are still gaps in our knowledge on how these two interact with metabolic pathways in vivo. Studying the cross-talk of these pathways has direct clinical implications as defects in cell division, signaling pathways, and metabolic homeostasis are frequently observed in liver diseases. In this review, we will focus on recent reports which describe various functions of cell cycle regulators in hepatic homeostasis. We will describe the interplay between the cell cycle and metabolism during liver regeneration after acute and chronic damage. We will focus our attention on non-alcoholic fatty liver disease, especially non-alcoholic steatohepatitis. The global incidence of non-alcoholic fatty liver disease is increasing exponentially. Therefore, understanding the interplay between cell cycle regulators and metabolism may lead to the discovery of novel therapeutic targets amenable to intervention.

Cellular and molecular basis of liver regeneration

Recent advances in genetics and genomics have reinvigorated the field of liver regeneration. It is now possible to combine lineage-tracing with genome-wide studies to genetically mark individual liver cells and their progenies and detect precise changes in their genome, transcriptome, and proteome under normal versus regenerative settings. The recent use of single-cell RNA sequencing methodologies in model organisms has, in some ways, transformed our understanding of the cellular and molecular biology of liver regeneration. Here, we review the latest strides in our knowledge of general principles that coordinate regeneration of the liver and reflect on some conflicting evidence and controversies surrounding this topic. We consider the prominent mechanisms that stimulate homeostasis-related vis-à-vis injury-driven regenerative responses, highlight the likely cellular sources/depots that reconstitute the liver following various injuries and discuss the extrinsic and intrinsic signals that direct liver cells to proliferate, de-differentiate, or trans-differentiate while the tissue recovers from acute or chronic damage.

Therapeutic targets for liver regeneration after acute severe injury: a preclinical overview

Introduction: Liver transplantation is the only viable treatment with a proven survival benefit for acute liver failure (ALF). Donor organ shortage is, however, a major hurdle; hence, alternative approaches that enable liver regeneration and target acute severe hepatocellular damage are necessary.Areas covered: This article sheds light on therapeutic targets for liver regeneration and considers their therapeutic potential. ALF following extensive hepatocyte damage and small-for-size syndrome (SFSS) are illuminated for the reader while the molecular mechanisms of liver regeneration are assessed in accordance with relevant therapeutic strategies. Furthermore, liver background parameters and predictive biomarkers that might associate with liver regeneration are reviewed.Expert opinion: There are established and novel experimental strategies for liver regeneration to prevent ALF resulting from SFSS. Granulocyte-colony stimulating factor (G-CSF) is a promising agent targeting liver regeneration after acute severe injury. Autophagy and hepatocyte senescence represent attractive new targets for liver regeneration in acute severe hepatic injury. Liver support strategies, including tissue engineering, constitute novel regenerative means; the success of this is dependent on stem cell research advances. However, there is no firm clinical evidence that these supportive strategies may alleviate hepatocellular damage until liver transplantation becomes available or successful self-liver regeneration occurs.

Metabolic syndrome and hepatic surgery

In Europe, the prevalence of metabolic syndrome (MS) has reached the endemic rate of 25%. Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of MS. Its definition is histological, bringing together the different lesions associated with hepatic steatosis (fat deposits on more than 5% of hepatocytes) without alcohol consumption and following exclusion of other causes. MS and NAFLD are implicated in the carcinogenesis of hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC). At present, HCC and ICC involving MS represent 15-20% and 20-30% respectively of indications for hepatic resection in HCC and ICC. Moreover, in the industrialized nations NAFLD is tending to become the most frequent indication for liver transplantation. MS patients combine the operative risk associated with their general condition and comorbidities and the risk associated with the presence and/or severity of NAFLD. Following hepatic resection in cases of HCC and ICC complicating MS, the morbidity rate ranges from 20 to 30%, and due to cardiovascular and infectious complications, post-transplantation mortality is heightened. The operative risk incurred by MS patients necessitates appropriate management including: (i) precise characterization of the subjacent liver; (ii) an accurately targeted approach privileging detection and optimization of treatment taking into account the relevant cardiovascular risk factors; (iii) a surgical strategy adapted to the histology of the underlying liver, with optimization of the volume of the remaining (postoperative) liver.

A Temporal Map of Gene Expression Pattern During Zebrafish Liver Regeneration

Zebrafish is increasingly being used to study liver injury and regeneration. However, very little is known about molecular players that respond to injury and those important for liver regeneration. We use a metronidazole nitroreductase (MTZ-nfsb)-based system to selectively ablate hepatocytes in adult zebrafish to create a model for liver injury and regeneration. In this study, we generate a comprehensive temporal map of gene expression changes during regeneration through RNA sequencing of liver samples at various stages of injury and regeneration. Analyzing these data, we find that soon after injury the immediate early transcription factor MYC induces a battery of genes that respond to the MTZ-induced ROS by activating oxido-reductase pathways and apoptosis machinery. Immediately after injury, liver cells downregulate many functional genes, including complement protein synthesis, bile acid, and lipid biosynthesis, in a concerted manner. At 6 days postinjury, we find a dramatic induction of cholesterol biosynthesis and protein folding machinery, with expression levels returning to predamage levels by 8 days, suggesting an important role for these pathways in liver regeneration. This chronological transcriptomic map of liver regeneration in zebrafish would serve as a framework for further studies in understanding, and for screening for compounds that augment liver regeneration.

High-Lard and High-Cholesterol Diet, but not High-Lard Diet, Leads to Metabolic Disorders in a Modified Dyslipidemia Model

BACKGROUND

In view of the increased global prevalence of cardiovascular and hepatic diseases, the diet lipid content and its relationship with the accumulation of fat in hepatocytes have been investigated as key factors in preventing these diseases.

OBJECTIVE

To evaluate the metabolic effects of a high-lard diet supplemented or not with cholesterol on a modified dyslipidemia model.

METHODS

We divided 24 adult male Wistar rats into three groups: standard diet (STD - 4% lipids), high-lard diet (HLD - 21% lard), and high-lard and high-cholesterol diet (HL/HCD - 20% lard, 1% cholesterol, 0.1% cholic acid). After six weeks of treatment, blood and liver were collected for biochemical (serum lipid profile and liver enzymes) and morphological analyses. Statistical analysis included one-way analysis of variance (ANOVA), followed by Tukey test for mean comparisons, and a 5% probability was considered statistically significant.

RESULTS

Animals fed HL/HCD showed increased total cholesterol, triacylglycerol, LDL-c, non-HDL-c, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) serum levels compared to those fed STD. In addition, the HL/HCD animals presented higher relative liver weight, with moderate macrovesicular hepatic steatosis and inflammatory infiltrate.

CONCLUSION

A high-fat diet with lard (20%) and cholesterol (1%) triggered dyslipidemia with severe liver damage in rats in a shorter experimental time than the previously reported models. The high-lard diet without supplementation of cholesterol led to body weight gain, but not to dyslipidemia.

Human Stem Cells Promote Liver Regeneration After Partial Hepatectomy in BALB/C Nude Mice

BACKGROUND

Mesenchymal stem cells (MSCs) have been suggested to augment liver regeneration after surgically and pharmacologically induced liver failure. To further investigate this we processed human bone marrow-derived MSC according to good manufacturing practice (GMP) and tested those cells for their modulatory capacities of metabolic alterations and liver regeneration after partial hepatectomy in BALB/c nude mice.

METHODS

Human MSCs were obtained by bone marrow aspiration of healthy donors as in a previously described GMP process. Transgenic GFP-MSCs were administered i.p. 24 h after 70% hepatectomy in BALB/c nude mice, whereas control mice received phosphate-buffered saline. Mice were sacrificed 2, 3, and 5 d after partial hepatectomy. Blood and organs were harvested and metabolic alterations as well as liver regeneration subsequently assessed by liver function tests, multianalyte profiling immunoassays, histology, and immunostaining.

RESULTS

Hepatocyte and sinusoidal endothelial cell proliferation were significantly increased after partial hepatectomy in mice receiving MSC compared to control mice (Hepatocyte postoperative day 3, P < 0.01; endothelial cell postoperative day 5, P < 0.05). Hepatocyte fat accumulation correlated inversely with hepatocyte proliferation (r² = 0.4064, P < 0.01) 2 d after partial hepatectomy, with mice receiving MSC being protected from severe fat accumulation. No GFP-positive cells could be detected in the samples. Serum levels of IL-6, HGF, and IL-10 were significantly decreased at day 3 in mice receiving MSC when compared to control mice (P < 0.05). Relative body weight loss was significantly attenuated after partial hepatectomy in mice receiving MSC (2 d and 3 d, both P < 0.001) with a trend toward a faster relative restoration of liver weight, when compared to control mice.

CONCLUSIONS

Human bone marrow-derived MSC attenuate metabolic alterations and improve liver regeneration after partial hepatectomy in BALB/c nude mice. Obtained results using GMP-processed human MSC suggest functional links between fat accumulation and hepatocyte proliferation, without any evidence for cellular homing. This study using GMP-proceeded MSC has important regulatory implications for an urgently needed translation into a clinical trial.

NAFLD Induction Delays Postoperative Liver Regeneration of ALPPS in Rats

BACKGROUND

Associating liver partition and portal vein ligation (ALPPS) is a promising two-step hepatectomy that is beneficial for accumulative regeneration of the future liver remnant (FLR) and avoids postoperative liver failure.

AIMS

Our study aimed to evaluate whether nonalcoholic fatty liver disease affected the liver regeneration induced by ALPPS.

METHODS

Sprague-Dawley rats fed a high-fat diet were used to construct the NAFLD model. ALPPS were performed, and blood and future liver remnant samples were collected at postoperative days 1 (POD1), POD3, and POD7.

RESULTS

The hepatic regeneration rate (HRR) of ALPPS was higher than that of portal vein ligation (PVL) at POD3 and POD7 (p < 0.05), and the number of Ki-67-positive hepatocytes (POD3) and CD68-positive Kupffer cells (POD7) per visual field was higher in the ALPPS group than in the PVL group (p < 0.05). The serum TNF-α, hepatocyte growth factor protein, and the serum IL-6 level were higher in the ALPPS group than in the PVL group at POD3 and POD7. Compared with those of the standard laboratory diet (SLD)-fed rats, the rats with NAFLD exhibited a decrease in the HRR, Ki-67-positive hepatocytes, and CD68-positive Kupffer cells in the FLR. The number of CD68-positive Kupffer cells was lower in rats with NAFLD than that in SLD-fed rats; noteworthily, the serum level of IL-6 and TNF-α changed dramatically after surgeries.

CONCLUSIONS

NAFLD induction delayed liver regeneration induced by the ALPPS procedure, which might be associated with hepatocyte proliferation and the number of Kupffer cells.

Liver-specific Repin1 deficiency impairs transient hepatic steatosis in liver regeneration

Transient hepatic steatosis upon liver resection supposes functional relationships between lipid metabolism and liver regeneration. Repin1 has been suggested as candidate gene for obesity and dyslipidemia by regulating key genes of lipid metabolism and lipid storage. Herein, we characterized the regenerative potential of mice with a hepatic deletion of Repin1 (LRep1−/−) after partial hepatectomy (PH) in order to determine the functional significance of Repin1 in liver regeneration. Lipid dynamics and the regenerative response were analyzed at various time points after PH. Hepatic Repin1 deficiency causes a significantly decreased transient hepatic lipid accumulation. Defects in lipid uptake, as analyzed by decreased expression of the fatty acid transporter Cd36 and Fatp5, may contribute to attenuated and shifted lipid accumulation, accompanied by altered extent and chronological sequence of liver cell proliferation in LRep1−/− mice. In vitro steatosis experiments with primary hepatocytes also revealed attenuated lipid accumulation and occurrence of smaller lipid droplets in Repin1-deficient cells, while no direct effect on proliferation in HepG2 cells was observed. Based on these results, we propose that hepatocellular Repin1 might be of functional significance for early accumulation of lipids in hepatocytes after PH, facilitating efficient progression of liver regeneration.

How Much Ischemia Can the Severely Steatotic Rat Liver Tolerate?

AIM

Steatotic liver is more susceptible to ischemia-reperfusion injury than is lean liver. Our aim was to investigate the ability of the severely steatotic rat liver to sustain ischemia.

MATERIALS AND METHODS

One hundred male Wistar rats aged 12-14 weeks were included. Fifty rats were given regular diet, while the rest were given a choline-free diet for 12-14 weeks to develop severe liver steatosis. Each group was divided into the following five subgroups: Sham-operated, and 5, 10, 15 and 20 minutes of continuous vascular inflow occlusion. Serum glutamic-oxaloacetic transaminase and serum glutamic-pyruvic transaminase levels were measured at 24 hours postoperatively and the animals were surveilled for 30 days.

RESULTS

Serum transaminase levels increased as the duration of ischemia increased in lean livers (p<0.0001), without a significant impact on animal survival. Similarly, serum transaminase levels increased as the duration of ischemia increased in severely steatotic livers (p<0.0001), reaching a plateau after 15 minutes of liver ischemia. Survival was significantly affected after the same cut-off point in rats with steatotic liver (p<0.0001). Serum transaminase levels were greater in severely rats with steatotic liver than in rats with lean liver, when they were adjusted for the duration of liver ischemia. Moreover, survival was reduced when serum transaminase levels surpassed the threshold of 2,000 IU/l (p<0.0001).

CONCLUSION

Severely steatotic rat liver can safely tolerate up to 10 minutes of continuous ischemia, with survival being affected after 15 minutes or more. On the other hand, lean rat liver can safely tolerate even 20 minutes of continuous ischemia.

Metabolic Remodeling during Liver Regeneration

Liver disease is linked to a decreased capacity of hepatocytes to divide. In addition, cellular metabolism is important for tissue homeostasis and regeneration. Since metabolic changes are a hallmark of liver disease, we investigated the connections between metabolism and cell division. We determined global metabolic changes at different stages of liver regeneration using a combination of integrated transcriptomic and metabolomic analyses with advanced functional redox in vivo imaging. Our data indicate that blocking hepatocyte division during regeneration leads to mitochondrial dysfunction and downregulation of oxidative pathways. This resulted in an increased redox ratio and hyperactivity of alanine transaminase allowing the production of alanine and α-ketoglutarate from pyruvate when mitochondrial functions are impaired. Our data suggests that during liver regeneration, cell division leads to hepatic metabolic remodeling. Moreover, we demonstrate that hepatocytes are equipped with a flexible metabolic machinery able to adapt dynamically to changes during tissue regeneration.

Cell size homeostasis: Metabolic control of growth and cell division

Joint regulation of growth rate and cell division rate determines cell size. Here we discuss how animal cells achieve cell size homeostasis potentially involving multiple signaling pathways converging at metabolic regulation of growth rate and cell cycle progression. While several models have been developed to explain cell size control, comparison of the two predominant models shows that size homeostasis is dependent on the ability to adjust cellular growth rate based on cell size. Consequently, maintenance of size homeostasis requires that larger cells can grow slower than small cells in relative terms. We review recent experimental evidence showing that such size adjustment occurs primarily at or immediately before the G1/S transition of the cell cycle. We further propose that bidirectional feedback between growth rate and size results in cell size sensing and discuss potential mechanisms how this may be accomplished.

Histopathological changes and onset of severe hepatic steatosis in rats fed a choline-free diet

Hepatic steatosis significantly increases morbidity and mortality associated with major liver surgery. Several rodent models of hepatic steatosis have been previously reported, which aimed to investigate the effect of various pharmaceutical agents and interventional procedures on the pathophysiology of steatotic liver. The aim of the present study was to investigate the time frame of severe hepatic steatosis in rats after they were fed a choline-free diet and any associated histopathological changes. The duration of feeding with a choline-free diet required to develop severe hepatic steatosis was investigated in Wistar rats. The severity of hepatic steatosis in liver specimens was evaluated at 8, 10, 12 and 14 weeks following the onset of the choline-free diet. Comparisons were made with rats receiving standardized laboratory food. Feeding rats for 12–13 weeks with a choline-free diet led to 66% fatty liver infiltration, which exceeded 68% after 14 weeks. Prior to 8 weeks, the fatty infiltration reached 43%, with a gradual increase revealing a stronger rate from 8–12 weeks and a gradual decline after 14 weeks. At 12–13 weeks the fatty infiltration was considered representative of severe hepatic steatosis. Macrovesicular fatty infiltration revealed a significant increase at a steady rate between 8 and 14 weeks, with evidence of the onset of lobular inflammation and steatohepatitis after 14 weeks of feeding with the choline-free diet. Microvesicular fatty infiltration demonstrated a lower growth rate between 8 and 12 weeks while maintaining a steady rate between 12 and 14 weeks. Mixed fatty infiltration maintained its steady rate of hepatic parenchyma from 8.8–9.5%. Rats fed with the standard laboratory diet did not demonstrate fatty infiltration >4.5%, so they did not develop hepatic steatosis. Developing an ideal model of hepatic steatosis is a particular challenge. The findings of the present study indicate that severe hepatic steatosis in rodents may lead to the development of steatohepatitis after feeding with a choline-free diet for at least 14 weeks. This model is of particular interest in experimental liver surgery and associated surgical maneuvers, and is easily reproducible.

Preoperative Chemotherapy on Functional Liver Regeneration for Colorectal Liver Metastases Assessed With 99mTc-GSA SPECT/CT Imaging

Objective:

To investigate the functional liver regeneration after chemotherapy and liver resection for colorectal liver metastases (CRLM).

Background/Purpose:

Preoperative chemotherapy followed by liver resection for CRLM has been increasing; however, its negative impact on liver regeneration remains unknown.

Methods:

From January 2009 to December 2013, we enrolled 40 selected patients who underwent major hepatectomy without viral hepatitis and severe liver fibrosis. CRLM patients with preoperative chemotherapy (CT-CRLM group, n = 12) and patients without preoperative chemotherapy (control group, n = 28) were evaluated. Liver volume (LV) and functional liver volume (FLV) was assessed using Tc-99m–labeled galactosyl human serum albumin (99mTc-GSA) scintigraphy, single-photon emission computed tomography (SPECT), CT-fused images. Preoperative, future remnant liver, and post 1-month values were compared.

Results:

Median course of preoperative chemotherapy was 8 (range: 6–16). Preoperative background factors were almost identical including resection rate and functional resection rate. In the CT-CRLM group and in the control group, the percentage increases in LV were 39.3% ± 29.0% and 23.2% ± 23.5% (P = 0.037), and FLV were 79.4% ± 43.1% and 57.0% ± 33.4% (P = 0.417), respectively; absolute differences in LV were 216.2 ± 155.7 cm3 and 148.7 ± 134.7 cm3 (P = 0.086) and FLV were 19.4% ± 8.5%/m2 and 17.4% ± 7.9%/m2 (P = 0.235), respectively. We found no obvious tendency for negative influence on liver functional regeneration by the preoperative regimens for CRLM.

Conclusions:

Several courses of preoperative chemotherapy may not affect functional liver regeneration for CRLM patients after major hepatectomy.

Short-term and long-term outcomes of liver transplantation using moderately and severely steatotic donor livers: A systematic review

BACKGROUND

The aim of this study was to perform a systemic review of the studies addressing the use of moderately and severely steatotic donor livers for liver transplantation.

METHODS

We searched the following electronic databases from January 1, 1989, to August 1, 2017: PubMed, EMBASE, Science Citation Index Expanded, and the Cochrane Library. In addition, reference lists were scanned to identify any additional reports. The quality of published papers was assessed. The main outcomes of the use of moderately and severely steatotic donor livers for liver transplantation, including primary nonfunction, short-term mortality, and long-term mortality, were extracted for pooled analysis.

RESULTS

Literature searches identified 16 studies that met the inclusion criteria. There were no randomized controlled studies, and all of the studies were retrospective or prospective case series. From a total of 3226 subjects (532 moderately and severely steatotic donor livers and 2694 controls), we found a significant increase in primary nonfunction [odds ratio (OR): 2.47, 95% confidence interval (95% CI): 1.44-4.27], and a trend of increase in 1-month patient mortality (OR: 1.90, 95% CI: 0.98-3.71) with the use of moderately and severely steatotic donor livers, whereas the 1-year mortality was relatively less influenced.

CONCLUSION

The use of moderately and severely steatotic livers is associated with unfavorable short-term outcomes, but long-term outcomes are relatively less influenced.

Mesenchymal Stem Cells Enhance Liver Regeneration via Improving Lipid Accumulation and Hippo Signaling

The liver has the potential to regenerate after injury. It is a challenge to improve liver regeneration (LR) after liver resection in clinical practice. Bone morrow-derived mesenchymal stem cells (MSCs) have shown to have a role in various liver diseases. To explore the effects of MSCs on LR, we established a model of 70% partial hepatectomy (PHx). Results revealed that infusion of MSCs could improve LR through enhancing cell proliferation and cell growth during the first 2 days after PHx, and MSCs could also restore liver synthesis function. Infusion of MSCs also improved liver lipid accumulation partly via mechanistic target of rapamycin (mTOR) signaling and enhanced lipid β-oxidation support energy for LR. Rapamycin-induced inhibition of mTOR decreased liver lipid accumulation at 24 h after PHx, leading to impaired LR. And after infusion of MSCs, a proinflammatory environment formed in the liver, evidenced by increased expression of IL-6 and IL-1β, and thus the STAT3 and Hippo-YAP pathways were activated to improve cell proliferation. Our results demonstrated the function of MSCs on LR after PHx and provided new evidence for stem cell therapy of liver diseases.

A predictive scoring system for insufficient liver hypertrophy after preoperative portal vein embolization

BACKGROUND

The factors which affect hypertrophy of the future liver remnant after portal vein embolization remain unclear. The aim of this study was to clarify the clinical factors affecting the hypertrophy rate after portal vein embolization and to develop a scoring system predicting insufficient liver hypertrophy.

METHODS

The cases of a total of 152 patients who underwent portal vein embolization of the right portal branch between 2006 and 2016 were reviewed retrospectively. The score to predict insufficient (<25%) hypertrophy was established based on logistic regression analyses of the clinical parameters before portal vein embolization.

RESULTS

After portal vein embolization, the future liver remnant volume, expressed as the median (range), significantly increased from 364 (151-801) mL, 33% (18%-54%), to 451 (242-866) mL, 42% (26%-65%). The median hypertrophy rate was 24% (-5% to 96%). A preoperative predictive scoring system for insufficient liver hypertrophy was constructed using the following 3 factors: an initial future liver remnant volume ≥35% (2 points), alkaline phosphatase ≥450 IU/dL (1 point), and cholinesterase <220 mg/dL (1 point). The constructed scoring system indicated the proportion of patients with insufficient liver hypertrophy (<25%) to be 6 out of 42 (14%) in the low-score group (0 points), 44 out of 77 (57%) in the medium-score group (1-2 points), and 30 out of 33 (91%) in the high-score group (3-4 points). The hypertrophy rate of future liver remnant was different among the 3 groups (low-score group, 38.9% [-2.4% to 81.4%]; medium-score group, 22.7% [-5.1% to 95.5%]; high-score group, 18.2% [2.4%-30.7%]) (P < .001).

CONCLUSION

The constructed scoring system was able to stratify patients before portal vein embolization according to the possibility of developing insufficient liver hypertrophy.

The ileal FGF15/19 to hepatic FGFR4 axis regulates liver regeneration after partial hepatectomy in mice

Fibroblast growth factor (FGF) has been considered to modulate liver regeneration (LR) after partial hepatectomy (PH) at the tissue level. Previous studies have demonstrated that FGF15 and FGF19 induce the activation of its receptor, FGF receptor 4 (FGFR4), which can promote hepatocellular carcinoma progression and regulate liver lipid metabolism. In this study, we aimed to explore the role of the ileal FGF15/19- hepatic FGFR4 axis in the LR after PH. Male C57BL/6 mice aged 8-12 weeks were partially hepatectomized and assessed for expression of ileal FGF15/19 to hepatic FGFR4 signaling. We used recombinant human FGF19 protein and a small interfering RNA (siRNA) of FGFR4 to regulate expression of the FGF15/19-FGFR4 axis in vitro and in vivo. The proliferation and cell cycle of hepatocytes, the expression levels of FGF15/19-FGFR4 downstream molecules, liver recovery, and lipid metabolism were assessed. We found that both ileal and serum FGF15 expression were upregulated and hepatic FGFR4 was activated after PH in mice. FGF15/19 promoted cell cycle progression, enhanced proliferation, and reduced hepatic lipid accumulation of hepatocytes both in vitro and in vivo. Furthermore, the proliferative effect and lipid regulatory properties of FGF15/19 were dependent on FGFR4 in hepatocytes. In addition, ileal FGF15/19-hepatic FGFR4 transduction during hepatocyte proliferation was regulated by extracellular regulated protein kinase (ERK) 1/2. In conclusion, the ileal FGF15/19 to hepatic FGFR4 axis is activated and promotes LR after PH in mice, supporting the potential of ileal FGF15/19 to hepatic FGFR4 axis-targeted therapy to enhance LR after PH.

Preserved liver regeneration capacity after partial hepatectomy in rats with non-alcoholic steatohepatitis

AIM

To evaluate the liver regeneration capacity (LRC) after partial hepatectomy (PH) in experimental non-alcoholic steatohepatitis (NASH).

METHODS

Fifty-four female rats were fed a high-fat, high-cholesterol diet (HFCD, 65% fat, 1% cholesterol) or standard diet (STD) for 16 wk. A 70% PH was performed and the animals were euthanised before PH or 2 or 5 d post-PH. LRC was evaluated using: The total number of Ki-67 positive hepatocytes in the caudate lobe, N(Ki-67, lobe) evaluated in a stereology-based design, the regenerated protein ratio (RPR), prothrombin-proconvertin ratio (PP), and mRNA expression of genes related to regeneration.

RESULTS

The HFCD NASH model showed significant steatosis with ballooning and inflammation, while no fibrosis was present. Mortality was similar in HFCD and STD animals following PH. HFCD groups were compared to respective STD groups and HFCD animals had a significantly elevated alanine transaminase at baseline (P < 0.001), as well as a significantly elevated bilirubin at day 2 after PH (P < 0.05). HFCD animals had a higher N(Ki-67, lobe) at baseline, (P < 0.0001), day 2 after PH (P = 0.06) and day 5 after PH (P < 0.025). We found no significant difference in RPR or PP neither 2 or 5 d post-PH. Expression of liver regeneration genes (e.g., hepatic growth factor) was higher at both day 2 and 5 post-PH in HFCD groups (P < 0.05).

CONCLUSION

NASH rats had a preserved LRC after hepatectomy when compared to STD rats. The methods and models of NASH are essential in understanding and evaluating LRC.

Loss of L-selectin-guided CD8+ , but not CD4+ , cells protects against ischemia reperfusion injury in a steatotic liver

Steatotic liver responds with increased hepatocellular injury when exposed to an ischemic-reperfusion insult. Increasing evidence supports the role of immune cells as key mediators of this injury in a normal (lean) state, but data about their role in a steatotic liver are practically nonexistent. The objective of the current study was to delineate the contribution of specific phenotypes of T cells and adhesion molecules in exacerbated cell death in steatotic liver injury. RNA sequencing was performed on isolated steatotic primary hepatocytes, and T-cell markers were assessed in hepatic lymphocytes after ischemia reperfusion injury (IRI) in high-fat diet (HFD)-fed mice. Cluster of differentiation 8 knockout (CD8^-/- ) and CD4^-/- mice along with CD8 and L-selectin antibody-treated mice were fed an HFD, and hepatocellular injury was assessed by histology, propidium iodide injection, and alanine aminotransferase after IRI. RNA sequencing demonstrated a strikingly differential gene profile in steatotic hepatocytes versus lean hepatocytes. After injury, the HFD liver showed increased necrosis, infiltrating CD8⁺ cells, alanine aminotransferase, and proinflammatory cytokines. Hepatic lymphocytes demonstrated increased CD8⁺ /CD62L⁺ (L-selectin) cells in HFD-fed mice after IRI. CD8^-/- mice and CD8-depleted C57BL/6 mice demonstrated significant protection from injury, which was not seen in CD4^-/- mice. L-selectin blockade also demonstrated significant hepatoprotection from IRI. L-selectin ligand MECA-79 was increased in HFD-fed mice undergoing IRI.

CONCLUSION

Blockade of CD8 and L-selectin, but not CD4, ameliorated hepatocellular injury, confirming that CD8⁺ cells are critical drivers of injury in a steatotic liver; this represents a therapeutic target in steatotic liver injury, underlining the importance of development of therapies specific to a steatotic liver. (Hepatology 2017;66:1258-1274).

PTEN Down-Regulation Promotes β-Oxidation to Fuel Hypertrophic Liver Growth After Hepatectomy in Mice

In regenerating liver, hepatocytes accumulate lipids before the major wave of parenchymal growth. This transient, regeneration-associated steatosis (TRAS) is required for liver recovery, but its purpose is unclear. The tumor suppressor phosphatase and tensin homolog (PTEN) is a key inhibitor of the protein kinase B/mammalian target of rapamycin axis that regulates growth and metabolic adaptations after hepatectomy. In quiescent liver, PTEN causes pathological steatosis when lost, whereas its role in regenerating liver remains unknown. Here, we show that PTEN down-regulation promotes liver growth in a TRAS-dependent way. In wild-type mice, PTEN reduction occurred after TRAS formation, persisted during its disappearance, and correlated with up-regulated β-oxidation at the expense of lipogenesis. Pharmacological modulation revealed an association of PTEN with TRAS turnover and hypertrophic liver growth. In liver-specific Pten^-/- mice shortly after induction of knockout, hypertrophic regeneration was accelerated and led to hepatomegaly. The resulting surplus liver mass was functional, as demonstrated by raised survival in a lethal model of resection-induced liver failure. Indirect calorimetry revealed lipid oxidation as the primary energy source early after hepatectomy. The shift from glucose to lipid usage was pronounced in Pten^-/- mice and correlated with the disappearance of TRAS. Partial inhibition of β-oxidation led to persisting TRAS in Pten^-/- mice and abrogated hypertrophic liver growth. PTEN down-regulation may promote β-oxidation through β-catenin, whereas hypertrophy was dependent on mammalian target of rapamycin complex 1.

CONCLUSION

PTEN down-regulation after hepatectomy promotes the burning of TRAS-derived lipids to fuel hypertrophic liver regeneration. Therefore, the anabolic function of PTEN deficiency in resting liver is transformed into catabolic activities upon tissue loss. These findings portray PTEN as a node coordinating liver growth with its energy demands and emphasize the need of lipids for regeneration. (Hepatology 2017;66:908-921).

Intermittent Ischemic Preconditioning Protects Against Hepatic Ischemia-Reperfusion Injury and Extensive Hepatectomy in Steatotic Rat Liver

BACKGROUND

Hepatic steatosis causes severe liver damage and has deleterious effects when associated with ischemia-reperfusion mechanisms. Ischemic preconditioning (IPC) protects lean liver against prolonged ischemia by improving micro-circulation and reducing lipid peroxidation. We investigated the effect of intermittent IPC on liver ischemia-reperfusion injury (IRI) and extensive hepatectomy in severe hepatic steatosis.

METHODS

Severe hepatic steatosis was performed by 12-14 weeks of choline-free diet in 108 Wistar rats. We induced 30-minute ischemia-reperfusion manipulations and extensive hepatectomy with or without prior IPC in steatotic livers and after 6 and 24 hours of reperfusion blood transaminases, and IL6, TNFα, NO and Lactate in blood and liver tissue were measured.

RESULTS

Steatotic rats subjected to hepatic ischemia-reperfusion alone after extensive hepatectomy, showed severe liver damage with significantly increased values of AST, ALT, TNFα and Lactate and significantly reduced IL6 and NO, while no one rat survived for more than 29 hours. On the contrary, steatotic rats subjected to intermittent IPC, 24 hours before ischemia-reperfusion, presented increased 30-day survival (67%), lower values of AST, ALT, TNFα and Lactate, and increased IL6 and NO levels. Simple and intermittent IPC manipulations, 1 hour before the IRI and extended hepatectomy, did not prolong survival more than 57 and 98 hours, respectively. Simple IPC, 24 hours before IRI and extended hepatectomy had the lowest possible survival (16.7%).

CONCLUSIONS

Hepatic steatosis and IRI after major liver surgery largely affect morbidity and mortality. Intermittent IPC, 24 hours before IRI and extensive hepatectomy, presents higher 30-day survival and improved liver function parameters.