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Background and Aims: Resmetirom, liver-directed thyroid-hormone receptor-β agonist, received approval for metabolic dysfunction-associated steatohepatitis (MASH) treatment. We assessed health-related quality of life (HRQL) in patients with MASH treated with resmetirom., Approach and Results: Patients with MASH/NASH without cirrhosis and with confirmed/suspected fibrosis were enrolled in a 54-month double-blind randomized placebo-controlled phase III clinical trial with serial biopsy assessments at baseline and week 52 (MAESTRO-NASH, NCT03900429). HRQL was assessed using Chronic Liver Disease Questionnaire-NASH (CLDQ-NAFLD) and Liver Disease Quality of Life (LDQOL). Baseline HRQL score changes by treatment group (resmetirom 80 mg, resmetirom 100 mg, or placebo) and histological response (improvement of fibrosis without worsening of NAS or resolution of MASH/NASH without worsening of fibrosis) were compared after 52 weeks. Included were 966 intention-to-treat patients: 323 received resmetirom 100 mg, 322 resmetirom 80 mg, and 321 placebo. By weeks 24 and 52, patients receiving 80 or 100 mg resmetirom experienced HRQL improvement in CLDQ-NAFLD Worry domain (mean +0.21 to +0.24, p < 0.05). At week 52, subjects who met histologic endpoints after treatment with resmetirom (100 mg and 80 mg pooled) experienced HRQL improvement in CLDQ-NAFLD Worry +0.46 (41% met minimal clinically important difference [MCID]), LDQOL domains: Role Emotional +3.0 (28% met MCID), Health Distress +8.1 (38% MCID), Stigma +3.5 (39% MCID), and total LDQOL +2.2 (35% MCID) (all p < 0.05). Similar improvements were noted in histologic responders from 100 mg or 80 mg resmetirom groups when separated-no improvements in placebo or nonresponders. Baseline F3 histologic responders had similar/more pronounced HRQL improvements., Conclusions: Patients with MASH/NASH with fibrosis improvement or the resolution of MASH with resmetirom experienced clinically meaningful and statistically significant HRQL improvements., (Copyright © 2024 American Association for the Study of Liver Diseases.)

Despite the growing incidence of obesity, knowledge of how this condition, as well as associated steatosis, affects liver regeneration remains scarce. Many previous studies have used models of steatohepatitis or obesity induced by genetic alterations. In contrast, our studies on liver regeneration have focused on the effects of obesity resulting solely from high amounts of fat in the diet. This model more closely reflects the detrimental effects of dietary habits responsible for increased morbidity due to obesity and its complications in well-developed Western societies. Impairment of liver regeneration was observed after partial hepatectomy in mice fed a high-fat diet. Fatty livers were more susceptible to posthepatectomy damage and failure. The underlying molecular mechanism was associated with increased inhibitor of nuclear factor-kappa B alpha (IkappaBalpha) expression, which inhibited nuclear factor-kappa B (NF-kappaB) activation and induction of its target genes, cyclin D1 and Bcl-xL, increasing sensitivity to apoptosis initiated by elevated tumor necrosis factor-alpha. In addition, since mice fed with a high-fat diet have higher leptin levels caused by increased adiposity, our work supports the hypothesis that the impairment of regeneration previously seen in genetically obese mice indeed results from liver steatosis rather than the disruption of leptin signaling. In conclusion, high fat in the diet impairs liver regeneration and predisposes steatotic livers to increased injury through IkappaBalpha overexpression and subsequent NF-kappaB inhibition.

Interleukin-6 (IL-6) is required for normal liver regeneration, but the specific cellular source of this growth factor is unknown. We investigated whether this signal originates from the resident macrophage, the Kupffer cell. Using a murine model of bone marrow transplantation, we replaced recipient bone marrow-derived cells, including Kupffer cells, with cells of donor genetic phenotype. Recipients deficient in IL-6 (IL-6(-/-)) were lethally irradiated, then rescued with 10(7) donor bone marrow cells capable of expressing IL-6 (IL-6(+/+)). Conversely, IL-6(+/+) recipients received IL-6(-/-) marrow. Successful engraftment was measured by the presence of the Y chromosome SRY locus in the livers of female recipients receiving male marrow, in situ IL-6 expression by Kupffer cells, and up-regulation of IL-6 in splenocytes after activation with lipopolysaccharide (LPS). Kupffer cell isolation in IL-6(-/-) females receiving IL-6(+/+) male marrow clearly showed the presence of the SRY locus and IL-6 disrupted allele, whereas males receiving female marrow demonstrated no SRY or IL-6 signals, confirming the extent of replacement. Replacement of these cells in IL-6(-/-) mice with IL-6(+/+) bone marrow successfully restored the regenerative response after partial hepatectomy (PHx) as indicated by signal transduction and activator of transcription 3 (STAT3) activation and hepatocyte DNA replication. Alternatively, complete replacement of Kupffer cells in IL-6(+/+) mice by transplantation with IL-6(-/-) cells significantly inhibited liver regeneration and was partially restored by administration of IL-6. This investigation demonstrates a paracrine mechanism by which cells of bone marrow origin, most likely Kupffer cells, regulate the regenerative capacity of the hepatocyte through IL-6 expression.

Liver regeneration following 70% partial hepatectomy leads to rapid activation of genes in the remnant liver. Interleukin-6 deficient (IL-6 -/-) mice have impaired liver regeneration and abnormalities in immediate early gene expression. In this study, the gene expression program in the IL-6 +/+ and -/- livers at 2 hours posthepatectomy was examined with a cDNA array representing 588 highly regulated mouse genes. Thirty-six percent of the 103 immediate early genes were induced differently in IL-6 +/+ compared with IL-6 -/- livers, implying regulation by IL-6. IL-6 treatment of the IL-6 -/- mice in the absence of hepatectomy induced a much smaller set of genes in the liver, suggesting that IL-6 cooperates with other hepatectomy-induced factors to activate the large number of genes. Northern blot analyses were used to verify gene expression data obtained from the arrays. The expression of urokinase type plasminogen activator receptor (uPAR) and plasminogen activator inhibitor-1 (PAI-1), critical components of the urokinase plasminogen activator (uPA) system, was lower and delayed in IL-6 -/- livers. Despite the fact that active uPAR/uPA complex is critical for hepatocyte growth factor (HGF) activation, no differences were detected between the IL-6 +/+ and -/- livers in HGF activation as measured by receptor phosphorylation. On the contrary, the mitogen-activated protein kinase (MAPK) pathway was activated in IL-6 +/+ livers early during regeneration but remarkably delayed in IL-6 -/- livers. Defective liver regeneration may be explained by the large number of gene activation pathways altered in IL-6 -/- livers and further supports the finding that IL-6 is necessary for normal liver regeneration.

Nuclear factor kappaB (NF-kappaB) is rapidly activated during liver regeneration following partial hepatectomy or carbon tetrachloride (CCl(4))-mediated liver injury and is felt to be important in the antiapoptotic and regenerative responses. After partial hepatectomy, livers of mice deficient in the p50 subunit of NF-kappaB (p50(-/-)) showed a loss of NF-kappaB and decreased STAT3 transcription factor DNA binding activities. However, nuclear levels of the NF-kappaB p65 subunit were increased and peaked earlier in p50(-/-) livers. Both messenger RNA and cytoplasmic protein levels of the NF-kappaB inhibitor IkappaBalpha were lower in p50(-/-) livers, potentially accounting for the increase in p65 protein. Small effects on gene expression posthepatectomy were observed in p50(-/-) livers, but no effects were seen on hepatocyte DNA synthetic or mitotic responses, serum enzyme levels, or overall liver mass restoration. After CCl(4) treatment, hepatocyte DNA synthesis and mitosis and serum enzyme levels were similar in p50(-/-) and p50(+/+) mice, and histologic analysis indicated a slight decrease in overall damage in p50(-/-) livers. After injection of Fas antibody, p50(-/-) livers showed an earlier onset of nuclear changes consistent with apoptosis. These data indicate that absence of p50 affects certain protein and gene activation pathways following partial hepatectomy, CCl(4), and Fas treatment but does not impair overall liver regeneration. Interleukin 6 (IL-6) levels were reduced but still adequate to support regeneration. We hypothesize that increased levels of the NF-kappaB p65 subunit in p50(-/-) livers may provide compensation for the absence of p50, thereby allowing normal liver regeneration and repair following liver injury.

Interleukin-6 null (IL-6-/-) mice have impaired liver regeneration and increased liver necrosis following partial hepatectomy that is corrected with IL-6 treatment. Following acute carbon tetrachloride (CCl(4)) treatment, we found that IL-6-/- mice developed increased hepatocellular injury and defective regeneration with significant blunting of signal transducer-and-activator of transcription protein 3 (STAT3) and nuclear factor-kappaB (NF-kappaB) activation and reduced hepatocyte DNA synthetic and mitotic responses. After CCl(4) treatment, unlike partial hepatectomy, increased hepatocyte apoptosis was noted in IL-6-/- livers. Pretreatment with IL-6 before CCl(4) reduced acute CCl(4) injury and apoptosis and accelerated regeneration in both IL-6+/+ and -/- livers. Repetitive doses of CCl(4) in the presence or absence of phenobarbital resulted in increased injury and fibrosis in IL-6 -/- compared with +/+ livers. After acute and chronic injury, IL-6-/- livers showed the protracted presence of alpha-smooth muscle actin associated with activated stellate cells, indicating a disturbed response in wound healing that progressed to fibrosis. These data provide evidence for an important role for IL-6 in reducing CCl(4)-induced acute and chronic liver injury and fibrosis.

The insulin-like growth factor binding protein-1 (IGFBP-1) gene is highly expressed in fetal, perinatal, and regenerating liver. Up-regulation is transcriptionally mediated in regenerating liver and occurs in the first few minutes to hours after partial hepatectomy. In transgenic mice a 970-bp region from -776 to +151 of the IGFBP-1 promoter was sufficient for tissue-specific and induced expression of the gene in fetal and hepatectomized livers. However weak and/or poorly regulated expression in some transgenic lines suggested the existence of other regulatory regions. Here, genomic clones containing large regions 5' of the mouse IGFBP-1 gene sequence were isolated, subcloned, and sequenced. Deoxyribonuclease I (DNaseI) hypersensitivity analyses identified clusters of tissue-specific nuclease-sensitive sites in the promoter region, -100 to -300, -2,300, -3,100, and -5,000 along with other weak sites. After partial hepatectomy, enhanced sensitivity and/or novel sites were detected in the -100/-300, -5,000, and -3,100 regions, the promoter region remaining the most hypersensitive. A subset of these sites was present in fetal and perinatal livers. Novel tissue-specific sites that interacted with C/EBP and hepatic nuclear factor 3 (HNF3) transcription factors were identified in the -3,100 region. A hepatectomy-induced DNA binding complex containing the transcription factor USF1 was identified within the -100 to -300 region of the promoter. These results suggested that a complex array of tissue-specific and hepatic proliferation-induced transcription factors combine to regulate both the proximal promoter and more distal regulatory elements of the IGFBP-1 gene.

Mutations in Jagged1, a Notch ligand, have been shown to result in Alagille syndrome (AGS), however, the causal link between haploinsufficiency of Jagged1 and intrahepatic ductal paucity is unknown. This survey was performed to determine the expression pattern of Jagged1 in the fetal and postnatal liver. Reverse transcription polymerase chain reaction (RT-PCR) showed Jagged1 expression in all samples studied including rat liver embryonic days 16 to 21, 1-day-old, 1-week-old, and 2-month-old adult rats. RT-PCR detected Jagged1 in total liver RNA extracted from cadaver organ donor samples from reduced human grafts and explanted native livers from a variety of pediatric disorders including AGS, biliary atresia, congenital hepatic fibrosis, sclerosing cholangitis, cystic fibrosis, fulminant hepatic failure, tyrosinemia, and chronic rejection. Immunohistochemistry showed Jagged1 expression in human fetal samples localized to the ductal plate from 14-week gestation onward. Expression in the postnatal liver was seen in biliary epithelium and zone 3 hepatocytes. In conclusion, these studies show that Jagged1 is expressed in the fetal and postnatal liver in health and disease. We show localization of expression by immunohistochemistry to ductal plate epithelium in human fetal samples and to the biliary epithelium and zone 3 hepatocytes in human postnatal samples. Our results show the localization of Jagged1 in fetal liver and demonstration of Jagged1 expression in postnatal rat and human liver specimens. Further studies of Jagged1 and the Notch signaling pathway are expected to elucidate mechanisms of the regulation of biliary epithelial growth and development.

Patients with hereditary tyrosinemia type 1 have a deficiency of fumarylacetoacetate hydrolase (FAH) and develop progressive hepatocellular dysfunction with a high risk of malignant transformation. Serum alpha-fetoprotein levels are frequently elevated in these patients; therefore, this commonly used marker of tumorigenesis is inadequate. To date, no literature exists describing the hepatic gene alterations in patients with this disease. We analyzed the expression of a panel of proliferation associated and liver-specific genes in the liver of a 33 month-old girl at the time of orthotopic liver transplantation. This study provides information that may be useful in developing markers for malignancy and understanding the pathogenesis of this disease. Gene expression patterns of two regenerating nodules and total liver from the patient with FAH deficiency were compared with control donor liver. Liver-specific and growth-induced genes with altered expression in the tyrosinemic liver included several functional classes: structural proteins (actin, thrombospondin), transcription factors (c-fos, egr-1, C/EBPalpha), liver-specific enzymes (glucose-6-phosphatase [G6Phase], and secreted factors (insulin-like growth factor binding protein 1 [GFBP-1]. Isolated macronodules demonstrated varied patterns of expression, suggesting that they do not form a homogeneous cellular environment. In the tyrosinemic liver, IGFBP-1 messenger RNA expression was high and G6Phase messenger RNA was not detectable. Although G6Phase and IGFBP-1 are coexpressed in regenerating liver, immunohistochemistry in the tyrosinemic liver demonstrated a mutually exclusive distribution for the two proteins in a tissue section with features of dysplasia. We propose that cells in these areas may have an aberrant transcription factor and growth factor "milieu" that leads to altered gene and protein expression. These molecular alterations are reflected in dysplastic histologic changes and may ultimately predispose to the development of malignancy.

The liver shows maximal cellular growth during fetal development and after partial hepatectomy. Exploring overlaps in gene expression patterns in these two types of hepatic growth may provide insight into common regulatory pathways. The expression of a large number of growth-induced and liver-specific genes induced in liver regeneration has been examined in the perinatal liver from several days prenatal to 4 weeks postnatal when the major growth phase of the liver ceases. As in liver regeneration, many growth-induced genes, such as PRL-1 and beta-actin, are expressed at a high level throughout the temporal course of liver development and correlate with the proliferative state. The level of fetal liver expression of these genes is similar to peak expression found in the regenerating liver, suggesting that common pathways of transcriptional regulation exist in the two types of proliferation. A subset of liver-restricted immediate-early genes including, IGFBP-1, CL-6, and glucose-6-phosphatase (G6Pase) are induced in regenerating liver and may be important in maintaining hepatic metabolism during regeneration. In developing liver, these genes are expressed primarily in the perinatal period but, unlike the regenerating liver, are not coinduced. For instance, at birth, G6Pase is induced, whereas CL-6 is downregulated. In situ analyses confirm that a proliferation associated gene PRL-1 is expressed in multiple cell types throughout the developing liver, whereas the expression of liver-specific genes is confined to hepatocytes. Taken together, these findings imply that significant similarities and differences in transcriptional regulation and hormonal milieu exist in liver during regeneration and development.(ABSTRACT TRUNCATED AT 250 WORDS)

Liver regeneration in response to partial hepatectomy is a physiological growth response observed in the intact animal. Understanding the early signals that trigger liver regeneration is of vital importance to understand the liver's response to injury. It has been observed that several growth factors and cytokines, including epidermal growth factor (EGF) and interleukin-6 (IL-6), can activate members of the signal transducers and activators of transcription (Stat) family of transcription factors resulting in tyrosine phosphorylation of these factors, nuclear translocation, and an active DNA binding transcriptional complex. Because Stat3 participates in the regulation of primary growth response genes, we wondered if it is induced in the early phase of liver regeneration. We found that Stat3 DNA-binding activity is increased in the remnant liver within 30 minutes of partial hepatectomy and peaks at more than 30-fold at 3 hours. This induction is not observed after sham surgery. The induction of Stat3 appears to be part of the initial response of the remnant liver to partial hepatectomy, because it occurs in the presence of cycloheximide-mediated protein synthesis blockade. Activation of Stat3 is unusual, because it extends beyond the immediate-early time period and remains near peak level at 5 hours posthepatectomy. Although insulin-treated H35 cells activate many of the same immediate-early genes as regenerating liver, Stat3 is not induced in these cells. Because Stat factors are known to be inactivated by protein tyrosine phosphatases (PTPase), we showed that a PTPase is able to eliminate the DNA binding of hepatic Stat3.(ABSTRACT TRUNCATED AT 250 WORDS)

Liver regeneration factor belongs to the leucine-zipper family of transcription factors. It was originally cloned and characterized through differential screening of a regenerating rat liver cDNA library. The mRNA for liver regeneration factor-1 is barely detectable in normal rat liver but is dramatically induced after two-thirds hepatectomy, with a peak 1 to 3 hr after surgery. The nature of the signaling molecule(s) for this rapid induction is not known. It has been suggested that the liver regeneration factor-1 protein product, through complex interactions with other transcription factors such as c-Jun and Jun-B, controls expression of genes that are required during the G1 phase of hepatic growth. Hepatocyte growth factor has been shown to be the most potent mitogen for hepatocytes in vitro and in vivo. Plasma levels of hepatocyte growth factor rapidly (within 30 min) increase after loss of hepatic parenchyma induced by partial hepatectomy or carbon tetrachloride treatment. It has been postulated that hepatocyte growth factor plays a crucial role in stimulating the hepatocyte to enter the cell cycle. In this communication, we report that addition of pure hepatocyte growth factor to primary cultures of rat hepatocytes in the absence of serum and insulin results in rapid and transient induction of liver regeneration factor-1 mRNA (more than 20-fold) with a peak of expression 1 hr after treatment. The levels of jun-B and c-fos mRNAs, which are also known to be induced during the early hours of liver regeneration, were also increased after treatment of isolated hepatocytes with hepatocyte growth factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin-like growth factor-binding protein-1s are important modulators of the insulin-like growth factors that may have both positive and negative effects on the ability of insulin-like growth factors to stimulate cell growth. The IGFBP-1 gene is one of the most highly induced immediate-early genes after partial hepatectomy. The IGFBP-1 gene is also expressed at a high level during fetal liver development and in response to nutritional changes and diabetes. Therefore it may have important roles in liver growth and metabolism. To begin to examine the regulation of this gene, we cloned and sequenced the entire mouse IGFBP-1 gene. Its structure is highly similar to that of the human gene, and, in addition to the exonic regions, the two genes are highly conserved in specific regions in the promoter and first intron. Analysis of this conservation allows us to predict important regulatory sites that define the tissue specific and insulin-mediated regulation of the gene and identify potential sites that might be important for the transcriptional induction during liver regeneration. The mouse gene is located on mouse chromosome 11; it is found at the boundary between regions in the mouse genome homologous to human chromosomes 22 and 7. We found IGFBP-1 mRNA in both parenchymal and nonparenchymal RNA after partial hepatectomy. Using in situ hybridization of IGFBP-1 mRNA in regenerating rat liver tissue, we demonstrated IGFBP-1 transcripts in several cell types. We found that IGFBP-1 gene induction after partial hepatectomy is paralleled by protein expression.(ABSTRACT TRUNCATED AT 250 WORDS)