Citrin deficiency: Does the reactivation of liver aralar-1 come into play and promote HCC development?

Hepatocellular carcinoma (HCC) is a longstanding issue in clinical practice and metabolic research. New clues in better understanding the pathogenesis of HCC might relate to the metabolic context in patients with citrin (aspartate-glutamate carrier 1) deficiency (CD). Because citrin-deficient liver (CDL) is subject to HCC, it represents a unique metabolic model to highlight the mechanisms of HCC promotion, offering different angles of study than the classical metabolic syndrome/obesity/non-alcoholic fatty liver disease (NAFLD)/HCC study axis. In turn, the metabolic features of HCC could shed light on the pathogenesis of CDL. Among these, HCC-induced re-activation of aralar-1 (aspartate-glutamate carrier 2), physiologically not expressed in the adult liver, might take place in CDL, so gene redundancy for mitochondrial aspartate-glutamate carriers would be exploited by the CDL. This proposed (aralar-1 re-activation) and known (citrate/malate cycle) adaptive mechanisms may substitute for the impaired function in CD and are consistent with the clinical remission stage of CD and CD improvement by medium-chain triglycerides (MCT). However, these metabolic adaptive benefits could also promote HCC development. In CD, as a result of PPARα down-regulation, liver mitochondrial fatty acid-derived acetyl-CoA would, like glucose-derived acetyl-CoA, be used for lipid anabolism and fuel nuclear acetylation events which might trigger aralar-1 re-activation as seen in non-CD HCC. A brief account of these metabolic events which might lead to aralar-1 re-activation in CDL is here given. Consistency of this account for CDL events further relies on the protective roles of PPARα and inhibition of mitochondrial and plasma membrane citrate transporters in non-CD HCC.

Plasma BCAA Changes in Patients With NAFLD Are Sex Dependent

CONTEXT

Plasma branched chain amino acid (BCAA) concentrations correlate positively with body mass index (BMI), measures of insulin resistance (IR), and severity of nonalcoholic fatty liver disease (NAFLD). Moreover, plasma BCAA concentrations also differ between the sexes, which display different susceptibilities to cardio-metabolic diseases.

OBJECTIVE

Assess whether plasma BCAA concentrations associate with NAFLD severity independently of BMI, IR, and sex.

PATIENTS

Patients visiting the obesity clinic of the Antwerp University Hospital were consecutively recruited from 2006 to 2014.

DESIGN AND SETTING

A cross-sectional study cohort of 112 obese patients (59 women and 53 men) was divided into 4 groups according to NAFLD severity. Groups were matched for sex, age, BMI, homeostatic model assessment of IR, and hemoglobin A1c.

MAIN OUTCOME MEASURES

Fasting plasma BCAA concentrations were measured by tandem mass spectrometry using the aTRAQ™ method.

RESULTS

In the study cohort, a modest positive correlation was observed between plasma BCAA concentrations and NAFLD severity, as well as a strong effect of sex on plasma BCAA levels. Subgroup analysis by sex revealed that while plasma BCAA concentrations increased with severity of NAFLD in women, they tended to decrease in men. Additionally, only women displayed significantly increased plasma BCAAs with increasing fibrosis.

CONCLUSION

Plasma BCAA concentrations display sex-dimorphic changes with increasing severity of NAFLD, independently of BMI, IR, and age. Additionally, plasma BCAA are associated with significant fibrosis in women, but not in men. These results highlight the importance of a careful consideration of sex as a major confounding factor in cross-sectional studies of NAFLD.

Citrulline and Monocyte-Derived Macrophage Reactivity before Conditioning Predict Acute Graft-versus-Host Disease

During conditioning, intestinal damage induces microbial translocation which primes macrophage reactivity and leads to donor-derived T cell stimulation. Little is known about the role of intestinal health and macrophage reactivity before conditioning in the development of acute graft-versus-host disease (aGVHD) in patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT). We assessed (1) citrulline, a surrogate marker of functional enterocyte mass and (2) circulating monocyte-derived macrophage reactivity, before allo-HCT. Forty-seven consecutive patients were prospectively included. Citrulline levels from blood samples withdrawn 30 days before transplantation were assessed using liquid chromatography combined with mass spectrometry. Monocyte-derived macrophages were isolated and incubated with 5 pathogen-associated molecular patterns: lipopolysaccharide, PamCSK4, flagellin, muramyl dipeptide, and curdlan. Multiplex fluorescent immunoassay on culture supernatant assessed levels of TNF-α, IL-1β, IL-6, and IL-10 in each condition. Citrulline and cytokine levels were analyzed relatively to aGVHD onset within 100 days after transplantation. Citrulline levels were lower in the aGVHD group (n = 20) than in the no-aGVHD group (n = 27) (P = .005). Conversely, IL-6 and IL-10 were greater in aGVHD group, especially after curdlan stimulation (P = .005 and P = .012). Citrulline levels ≤20 µmol/L, IL-6 ≥ 332 pg/mL, and IL-10 ≥ 90 pg/mL were associated with aGVHD development (log-rank test, P = .002, P = .041, and P < .0001, respectively). In multivariate analysis, IL-10 ≥ 90 pg/mL, myeloablative conditioning, and citrulline ≤20 µmol/L remained independent factors of aGVHD development (hazard ratio [HR],  8.18, P = .0003; HR, 4.28, P = .006; and HR, 4.43, P = .01, respectively). Preconditioning citrulline and monocyte-derived macrophage reactivity are objective surrogate markers suitable to identify patients at risk of developing aGVHD. This work highlights the influence of preconditioning status in aGVHD development.

The lacdiNAc-specific adhesin LabA mediates adhesion of Helicobacter pylori to human gastric mucosa

Adhesion of Helicobacter pylori to the gastric mucosa is a necessary prerequisite for the pathogenesis of H. pylori-related diseases. In this study, we investigated the GalNAcβ1-4GlcNAc motif (also known as N,N'-diacetyllactosediamine [lacdiNAc]) carried by MUC5AC gastric mucins as the target for bacterial binding to the human gastric mucosa. The expression of LacdiNAc carried by gastric mucins was correlated with H. pylori localization, and all strains tested adhered significantly to this motif. Proteomic analysis and mutant construction allowed the identification of a yet uncharacterized bacterial adhesin, LabA, which specifically recognizes lacdiNAc. These findings unravel a target of adhesion for H. pylori in addition to moieties recognized by the well-characterized adhesins BabA and SabA. Localization of the LabA target, restricted to the gastric mucosa, suggests a plausible explanation for the tissue tropism of these bacteria. These results pave the way for the development of alternative strategies against H. pylori infection, using adherence inhibitors.