Prednisolone but not infliximab aggravates the upregulated hepatic nitrogen elimination in patients with active inflammatory bowel disease

Early normalization of reduced urea synthesis capacity after direct-acting antiviral therapy in hepatitis C cirrhosis

Laursen TL, Sandahl TD, Kazankov K, Eriksen PL, Kristensen LH, Holmboe CH, Laursen AL, Vilstrup H, Grønbæk H. Early normalization of reduced urea synthesis capacity after direct-acting antiviral therapy in hepatitis C cirrhosis. Am J Physiol Gastrointest Liver Physiol 319: G151-G156, 2020. First published June 29, 2020; doi:10.1152/ajpgi.00128.2020.-Effects of direct-acting antiviral (DAA) treatment of chronic hepatitis C (CHC) cirrhosis on metabolic liver function are unknown but important for prognosis. Ureagenesis is an essential metabolic liver function involved in whole body nitrogen homeostasis. We aimed to investigate the ureagenesis capacity before and immediately after DAA therapy and relate the findings to hepatic inflammation and structural changes. In an observational before-and-after intervention study, the ureagenesis capacity was quantified by functional hepatic nitrogen clearance (FHNC) in 9 CHC patients with cirrhosis and 10 healthy volunteers. Hepatic inflammation was evaluated by alanine aminotransferase (ALT) and the macrophage activation markers sCD163 and sMR. Structural changes were estimated as liver stiffness and by portal hypertension as the hepatic venous pressure gradient (HVPG). Before treatment, the FHNC in the patients was half of the controls [16.4 L/h (8.2-24.5) vs. 33.4 (29.2-37.6), P = 0.0004]; after successful DAA treatment, it normalized [28.4 (15.9-40.9), P = 0.008 vs. baseline]. DAA treatment normalized ALT (P < 0.0001) and decreased the elevated sCD163 from 5.6 mg/L (3.5-7.7) to 3.4 (2-0-4.8) (P < 0.001) and sMR from 0.35 mg/L (0.21-0.49) to 0.31 (0.17-0.45) (P < 0.01). Liver stiffness fell by 30% (P < 0.05) but remained over the cirrhosis threshold. HVPG was not affected (P = 0.59). DAA treatment restored the severely reduced ureagenesis capacity, along with amelioration of hepatic inflammation but without normalization of other cirrhosis characteristics. Our findings indicate that the anti-inflammatory effect of virus eradication independent of hepatic structural effects rapidly improves metabolic dysfunction. We suggest this effect to be an important early onset part of the expected clinical DAA treatment benefit.NEW & NOTEWORTHY Antiviral treatment of chronic hepatitis C restores the liver's reduced capacity to produce urea along with an improvement in liver inflammation without immediate effects on structural liver changes. The effect is suggested to be an important early onset part of the expected clinical treatment benefit.

Non-alcoholic fatty liver disease alters expression of genes governing hepatic nitrogen conversion

BACKGROUND & AIMS

We recently showed that the functional capacity for ureagenesis is deficient in non-alcoholic fatty liver disease (NAFLD) patients. The aim of this study was to assess expression of urea cycle-related genes to elucidate a possible gene regulatory basis to the functional problem.

METHODS

Liver mRNA expression analyses within the gene pathway governing hepatic nitrogen conversion were performed in 20 non-diabetic, biopsy-proven NAFLD patients (8 simple steatosis; 12 non-alcoholic steatohepatitis [NASH]) and 12 obese and 14 lean healthy individuals. Sixteen NAFLD patients were included for gene expression validation. Relationship between gene expressions and functional capacity for ureagenesis was described.

RESULTS

Gene expression of most urea cycle-related enzymes were downregulated in NAFLD vs both control groups; markedly so for the urea cycle flux-generating carbamoyl phosphate synthetase (CPS1) (~3.5-fold, P < .0001). In NASH, CPS1 downregulation paralleled the deficit in ureagenesis (P = .03). Additionally, expression of several genes involved in amino acid uptake and degradation, and the glucagon receptor gene, were downregulated in NAFLD. Conversely, glutamine synthetase (GS) expression increased >1.5-fold (P ≤ .03), inversely related to CPS1 expression (P = .004).

CONCLUSIONS

NAFLD downregulated the expression of urea cycle-related genes. Downregulation of urea cycle flux-generating CPS1 correlated with the loss of functional capacity for ureagenesis in NASH. On gene level, these changes coincided with an increase in the major ammonia scavenging enzyme GS. The effects seemed related to a fatty liver as such rather than NASH or obesity. The findings support gene regulatory mechanisms involved in the deficient ureagenesis of NAFLD, but it remains unexplained how hepatocyte fat accumulation exerts these effects.

The IGF system in patients with inflammatory bowel disease treated with prednisolone or infliximab: potential role of the stanniocalcin-2 / PAPP-A / IGFBP-4 axis

Background

Patients with inflammatory bowel disease (IBD) present with reduced serum insulin-like growth factor I (IGF-I). Anti-inflammatory treatment with prednisolone or infliximab ameliorates symptoms and increases circulating IGF-I, but prednisolone induces catabolism, whereas infliximab may promote protein synthesis. Recently, stanniocalcin-2 (STC2) was discovered as a novel inhibitor of the enzyme pregnancy-associated plasma protein-A (PAPP-A), which modulates IGF-I activity. PAPP-A can cleave IGF binding protein-4 (IGFBP-4), upon which IGF-I is liberated. We hypothesized that prednisolone and infliximab exert different effects on levels of STC2, PAPP-A, and IGFBP-4, thereby explaining the distinct metabolic effects of prednisolone and infliximab.

Methods

Thirty-eight patients with active IBD treated with either prednisolone (n = 17) or infliximab (n = 21) were examined before and after 7 days of treatment. Circulating levels of IGF-I, IGF-II, IGFBP-3, PAPP-A, and STC2 were measured by immunoassays. Intact IGFBP-4 and two IGFBP-4 fragments were determined by a novel immunoassay. Bioactive IGF was assessed by cell-based IGF receptor activation assay. Concentrations of IGFBP-4, PAPP-A, and STC2 on day 0 and 7 were compared to healthy control subjects.

Results

Following seven days of prednisolone treatment, total and bioactive IGF-I were increased (p < 0.001 and p < 0.05, respectively). Upon infliximab treatment, total IGF-I levels were augmented (p < 0.05), yet IGF bioactivity remained unaltered. Intact IGFBP-4 and the two IGFBP-4 fragments generated upon cleavage by PAPP-A were all decreased following treatment with either prednisolone or infliximab (all p < 0.05). PAPP-A levels were only increased by infliximab (p = 0.005), whereas the inhibitor STC2 did not respond to any of the treatments.

Conclusion

IGF-I and IGFBP-4 concentrations were markedly altered in patients with IBD and near-normalized with disease remission following treatment with prednisolone or infliximab. Thus, IGFBP-4 may modulate IGF bioavailability in IBD. The effect of immunosuppression did not appear to extend beyond the regulation of IGF and IGFBP-4, as neither PAPP-A nor STC2 were discernibly affected.

Trial registration

ClinicalTrials.gov: NCT00955123. Date of registration: August 7, 2009 (retrospectively registered).

Time course of compromised urea synthesis in patients with alcoholic hepatitis

OBJECTIVES

Alcoholic hepatitis (AH) markedly decreases the urea synthesis capacity. We aimed to investigate the time course of this compromised essential liver function in patients with AH and its relation to treatment and survival.

MATERIALS AND METHODS

Thirty patients with AH were included in a prospective cohort study. We measured the substrate-independent urea synthesis capacity, i.e., the functional hepatic nitrogen clearance (FHNC), in the patients at study entry and again at three months (survivors/available: n = 17). Patients with severe disease (Glasgow Alcoholic Hepatitis Score ≥9, n = 17) were randomized to receive either prednisolone or pentoxifylline and were in addition examined after 14 days (n = 9).

RESULTS

FHNC (normal range = 25-45 L/h) was markedly decreased at study entry (median = 5.6 (IQR = 3.0-9.6) L/h) and increased by three-fold in survivors at three months (15.1 (12.0-22.9) L/h; p < .001). In patients with severe AH, FHNC was also increased after 14 days of pharmacologic treatment and showed the greatest increase in the patients taking prednisolone (prednisolone 25.4 (20.6-26.2) L/h vs. pentoxifylline 12.3 (8.0-15.3) L/h; p = .05). FHNC at study entry was lower in 90-day non-survivors than in survivors (p = .04).

CONCLUSIONS

The decrease in the urea synthesis capacity in patients with AH was the most marked in short-term non-survivors and partly recovered in survivors at three months. In patients on pharmacologic treatment, recovery was observed already after 14 days, and it was nearly complete in those on prednisolone. Thus, metabolic liver failure in AH seems to be prognostically important, is potentially reversible, and may recover more rapidly following treatment with prednisolone.

Safety of treatments for inflammatory bowel disease: Clinical practice guidelines of the Italian Group for the Study of Inflammatory Bowel Disease (IG-IBD)

Inflammatory bowel diseases are chronic conditions of unknown etiology, showing a growing incidence and prevalence in several countries, including Italy. Although the etiology of Crohn's disease and ulcerative colitis is unknown, due to the current knowledge regarding their pathogenesis, effective treatment strategies have been developed. Several guidelines are available regarding the efficacy and safety of available drug treatments for inflammatory bowel diseases. Nevertheless, national guidelines provide additional information adapted to local feasibility, costs and legal issues related to the use of the same drugs. These observations prompted the Italian Group for the Study of Inflammatory Bowel Disease (IG-IBD) to establish Italian guidelines on the safety of currently available treatments for Crohn's disease and ulcerative colitis. These guidelines discuss the use of aminosalicylates, systemic and low bioavailability corticosteroids, antibiotics (metronidazole, ciprofloxacin, rifaximin), thiopurines, methotrexate, cyclosporine A, TNFα antagonists, vedolizumab, and combination therapies. These guidelines are based on current knowledge derived from evidence-based medicine coupled with clinical experience of a national working group.

Alcoholic Hepatitis Markedly Decreases the Capacity for Urea Synthesis

Background and Aim

Data on quantitative metabolic liver functions in the life-threatening disease alcoholic hepatitis are scarce. Urea synthesis is an essential metabolic liver function that plays a key regulatory role in nitrogen homeostasis. The urea synthesis capacity decreases in patients with compromised liver function, whereas it increases in patients with inflammation. Alcoholic hepatitis involves both mechanisms, but how these opposite effects are balanced remains unclear. Our aim was to investigate how alcoholic hepatitis affects the capacity for urea synthesis. We related these findings to another measure of metabolic liver function, the galactose elimination capacity (GEC), as well as to clinical disease severity.

Methods

We included 20 patients with alcoholic hepatitis and 7 healthy controls. The urea synthesis capacity was quantified by the functional hepatic nitrogen clearance (FHNC), i.e., the slope of the linear relationship between the blood α-amino nitrogen concentration and urea nitrogen synthesis rate during alanine infusion. The GEC was determined using blood concentration decay curves after intravenous bolus injection of galactose. Clinical disease severity was assessed by the Glasgow Alcoholic Hepatitis Score and Model for End-Stage Liver Disease (MELD) score.

Results

The FHNC was markedly decreased in the alcoholic hepatitis patients compared with the healthy controls (7.2±4.9 L/h vs. 37.4±6.8 L/h, P<0.01), and the largest decrease was observed in those with severe alcoholic hepatitis (4.9±3.6 L/h vs. 9.9±4.9 L/h, P<0.05). The GEC was less markedly reduced than the FHNC. A negative correlation was detected between the FHNC and MELD score (rho = -0.49, P<0.05).

Conclusions

Alcoholic hepatitis markedly decreases the urea synthesis capacity. This decrease is associated with an increase in clinical disease severity. Thus, the metabolic failure in alcoholic hepatitis prevails such that the liver cannot adequately perform the metabolic up-regulation observed in other stressful states, including extrahepatic inflammation, which may contribute to the patients’ poor prognosis.

GC-MS metabolomics on PPARα-dependent exacerbation of colitis

Fenofibrate, a peroxisome proliferator-activated receptor α (PPARα) agonist, was found to exacerbate inflammation and tissue injury in experimental acute colitis mice. Through lipidomics analysis, bioactive sphingolipids were significantly up-regulated in the colitis group. In this study, to provide further insight into the PPARα-dependent exacerbation of colitis, gas chromatography-mass spectrometry (GC/MS) based metabolomics was employed to investigate the serum and colon of dextran sulfate sodium (DSS)-induced colitis mice treated with fenofibrate, with particular emphasis on changes in low-molecular-weight metabolites. With the aid of multivariate analysis and metabolic pathway analysis, potential metabolite markers in the amino acid metabolism, urea cycle, purine metabolism, and citrate cycle were highlighted, such as glycine, serine, threonine, malic acid, isocitric acid, uric acid, and urea. The level changes of these metabolites in either serum or colons of colitis mice were further potentiated following fenofibrate treatment. Accordingly, the expression of threonine aldolase and phosphoserine aminotransferase 1 was significantly up-regulated in colitis mice and further potentiated in fenofibrate/DSS-treated mice. It was revealed that beyond the control of lipid metabolism, PPARα also shows effects on the above pathways, resulting in enhanced protein catabolism and energy expenditure, increased bioactive sphingolipid metabolism and proinflammatory state, which were possibly related to the exacerbated colitis.