The altered serum lipidome and its diagnostic potential for Non-Alcoholic Fatty Liver (NAFL)-associated hepatocellular carcinoma.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is affecting more people globally. Indeed, NAFLD is a spectrum of metabolic dysfunctions that can progress to hepatocellular carcinoma (NAFLD-HCC). This development can occur in a non-cirrhotic liver and thus, often lack clinical surveillance. The aim of this study was to develop non-invasive surveillance method for NAFLD-HCC. METHODS: Using comprehensive ultra-high-performance liquid chromatography mass-spectrometry, we investigated 1,295 metabolites in serum from 249 patients. Area under the receiver operating characteristic curve was calculated for all detected metabolites and used to establish their diagnostic potential. Logistic regression analysis was used to establish the diagnostic score. FINDINGS: We show that NAFLD-HCC is characterised by a complete rearrangement of the serum lipidome, which distinguishes NAFLD-HCC from non-cancerous individuals and other HCC patients. We used machine learning to build a diagnostic model for NAFLD-HCC. We quantified predictive metabolites and developed the NAFLD-HCC Diagnostic Score (NHDS), presenting superior diagnostic potential compared to alpha-fetoprotein (AFP). Patients' metabolic landscapes show a progressive depletion in unsaturated fatty acids and acylcarnitines during transformation. Upregulation of fatty acid transporters in NAFLD-HCC tumours contribute to fatty acid depletion in the serum. INTERPRETATION: NAFLD-HCC patients can be efficiently distinguished by serum metabolic alterations from the healthy population and from HCC patients related to other aetiologies (alcohol and viral hepatitis). Our model can be used for non-invasive surveillance of individuals with metabolic syndrome(s), allowing for early detection of NAFLD-HCC. Therefore, serum metabolomics may provide valuable insight to monitor patients at risk, including morbidly obese, diabetics, and NAFLD patients. FUNDING: The funding sources for this study had no role in study design, data collection, data analyses, interpretation or writing of the report as it is presented herein.

MECHANISMS IN ENDOCRINOLOGY: The physiology of neuronostatin.

In 2008, the first evidence of a new hormone called neuronostatin was published. The hormone was discovered using a bioinformatic method and found to originate from the same preprohormone as somatostatin. This small peptide hormone of 13 amino acids and a C-terminal amidation was soon found to exert pleiotropic physiological effects. In animal studies, neuronostatin has been shown to reduce food intake and delay gastric emptying and gastrointestinal transit. Furthermore, neuronostatin has been shown to affect glucose metabolism by increasing glucagon secretion during situations when glucose concentrations are low. Additionally, neuronostatin has been shown to affect neural tissue and cardiomyocytes by suppressing cardiac contractility. The effects of neuronostatin have not yet been delineated in humans, but if the effects found in animal studies translate to humans it could position neuronostatin as a promising target in the treatment of obesity, hypertension and diabetes. In this review, we describe the discovery of neuronostatin and the current understanding of its physiological role and potential therapeutic applicability.

Human translatability of the GAN diet-induced obese mouse model of non-alcoholic steatohepatitis.

BACKGROUND: Animal models of non-alcoholic steatohepatitis (NASH) are important tools in preclinical research and drug discovery. Gubra-Amylin NASH (GAN) diet-induced obese (DIO) mice represent a model of fibrosing NASH. The present study directly assessed the clinical translatability of the model by head-to-head comparison of liver biopsy histological and transcriptome changes in GAN DIO-NASH mouse and human NASH patients. METHODS: C57Bl/6 J mice were fed chow or the GAN diet rich in saturated fat (40%), fructose (22%) and cholesterol (2%) for ≥38 weeks. Metabolic parameters as well as plasma and liver biomarkers were assessed. Liver biopsy histology and transcriptome signatures were compared to samples from human lean individuals and patients diagnosed with NASH. RESULTS: Liver lesions in GAN DIO-NASH mice showed similar morphological characteristics compared to the NASH patient validation set, including macrosteatosis, lobular inflammation, hepatocyte ballooning degeneration and periportal/perisinusoidal fibrosis. Histomorphometric analysis indicated comparable increases in markers of hepatic lipid accumulation, inflammation and collagen deposition in GAN DIO-NASH mice and NASH patient samples. Liver biopsies from GAN DIO-NASH mice and NASH patients showed comparable dynamics in several gene expression pathways involved in NASH pathogenesis. Consistent with the clinical features of NASH, GAN DIO-NASH mice demonstrated key components of the metabolic syndrome, including obesity and impaired glucose tolerance. CONCLUSIONS: The GAN DIO-NASH mouse model demonstrates good clinical translatability with respect to the histopathological, transcriptional and metabolic aspects of the human disease, highlighting the suitability of the GAN DIO-NASH mouse model for identifying therapeutic targets and characterizing novel drug therapies for NASH.

Glucagon Resistance at the Level of Amino Acid Turnover in Obese Subjects With Hepatic Steatosis.

Glucagon secretion is regulated by circulating glucose, but it has turned out that amino acids also play an important role and that hepatic amino acid metabolism and glucagon are linked in a mutual feedback cycle, the liver-α-cell axis. On the basis of this knowledge, we hypothesized that hepatic steatosis might impair glucagon's action on hepatic amino acid metabolism and lead to hyperaminoacidemia and hyperglucagonemia. We subjected 15 healthy lean and 15 obese steatotic male participants to a pancreatic clamp with somatostatin and evaluated hepatic glucose and amino acid metabolism when glucagon was at basal levels and at high physiological levels. The degree of steatosis was evaluated from liver biopsy specimens. Total RNA sequencing of liver biopsy specimens from the obese steatotic individuals revealed perturbations in the expression of genes predominantly involved in amino acid metabolism. This group was characterized by fasting hyperglucagonemia, hyperaminoacidemia, and no lowering of amino acid levels in response to high levels of glucagon. Endogenous glucose production was similar between lean and obese individuals. Our results suggest that hepatic steatosis causes resistance to the effect of glucagon on amino acid metabolism. This results in increased amino acid concentrations and increased glucagon secretion, providing a likely explanation for fatty liver-associated hyperglucagonemia.

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.