Human apolipoprotein A-IV reduces gastric acid secretion and diminishes ulcer formation in transgenic mice

Serum protein isoform profiles indicate the progression of hepatitis C virus-induced liver diseases

Biomarkers that enable an accurate diagnosis of hepatitis C virus (HCV)-induced liver diseases are necessary to prevent subsequent patient morbidity and suffering from the onset of hepatocellular carcinoma (HCC). In particular, the identification of novel biomarkers for liver cirrhosis (LC) will be an important new diagnostic tool since more than 70% of HCV-induced LCs are destined to develop into HCC. In our current study, we performed a search for new serological protein biomarkers of HCV-induced chronic hepatitis (CH), LC and HCC, using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). The disease-affected spots were subsequently identified as isoforms of protein components of haptoglobin, transthyretin, the haptoglobin α-chain and apolipoprotein A-IV (apo A-IV), and in specific instances were significantly reduced in LC (p<0.001) and HCC (p<0.01), compared with CH patients. We further examined these isoforms by receiver operating characteristics (ROC) curve analysis and found that they showed high area under ROC curve (AUC) values of more than 0.8 between CH and LC, suggesting that they are appropriate markers that could be utilized to discriminate LC from CH. In conclusion, protein variants in serum that arise as a result of post-translational modifications prove to be useful biomarkers for the accurate diagnosis of specific liver diseases.

Apolipoprotein A-IV is involved in detection of lipid in the rat intestine

Long chain triglyceride (>C12) in the intestinal lumen potently inhibits gastric emptying and acid secretion via the vagal afferent pathway. While the mechanism of inhibition involves the formation of chylomicrons, the essential role of the apolipoprotein apo A-IV is unclear. Using apo A-IV(-/-) mice, we tested the hypothesis that inhibition of gastric emptying and gastric acid secretion in response to dietary lipid is dependent upon apo A-IV. As measured by nuclear scintigraphy in awake mice, gastric emptying of an ingested whole-egg meal was significantly faster in apo A-IV(-/-) knockout versus A-IV(+/+) controls (34 +/- 1 versus 54 +/- 3 min, P < 0.0001). In anaesthetized A-IV(+/+) mice, meal-stimulated gastric acid secretion was 59% inhibited by intestinal lipid infusion; this was abolished in apo A-IV(-/-) mice. Oral gavage of lipid in awake mice activated neurones throughout the nucleus of the solitary tract (NTS) in A-IV(+/+) mice, measured by immunohistochemical localization of Fos protein expression. However, in the mid region of the NTS (bregma -7.32 to -7.76 mm), Fos expression in response to intestinal lipid was significantly decreased by 50% in apo A-IV(-/-) mice compared to A-IV(+/+) controls. We conclude that activation of the vagal afferent pathway and inhibition of gastric function in response to dietary lipid is partly dependent upon apo A-IV.