I. Zvibel

Dipeptidyl Peptidase 4-Deficient Rats Have Improved Bile Secretory Function in High Fat Diet-Induced Steatosis

Background/AimsRodent obesity models have been shown to display impaired bile secretory functions. We have shown that glucagon-like peptide 1 (GLP-1) attenuates hepatic lipogenesis, and in the present study we investigated whether GLP-1 also improves high fat diet-associated cholestatic injury.MethodsWild type (WT) and dipeptidyl peptidase 4-deficient rats (DPP4-) with chronic elevated serum levels of active GLP-1 were fed regular chow and a Western diet for 2xa0months. Primary hepatocytes were used to assess GLP-1 effects on mRNA expression and transcription of genes encoding bile acid synthesis enzymes and transporters.ResultsDPP4- exhibited attenuated liver injury as expressed by lower serum AST and ALT after 2xa0months of a Western diet. In addition, DPP4- had better insulin sensitivity, lower serum triglycerides, cholesterol and bile acids. Hepatic expression of cyp7A1, the rate limiting enzyme in conversion of cholesterol into bile acids, was strongly attenuated in DPP4- fed with a Western diet. Moreover, hepatic expression of bile transporter, ABCB11, was increased, facilitating a higher rate of bile secretion. Mechanistically, we showed that GLP-1 directly reduced basal and LXR-induced cyp7A1 mRNA expression and suppressed cyp7A1 transcription in transient transfection assays in primary hepatocytes. However, GLP-1 and its analog exendin 4 also induced mRNA expression of bile acid transporter ABCC3 in primary rat hepatocyte cultures.ConclusionsOur data suggest that GLP-1 analogs may serve as a novel therapeutic drug to alleviate obesity-induced liver injury by reducing bile acid synthesis and improving liver bile secretory function.

Transcriptional profiling identifies genes induced by hepatocyte-derived extracellular matrix in metastatic human colorectal cancer cell lines

The milieu of the liver, and in particular hepatocyte-derived extracellular matrix (hECM), is a critical factor regulating development of liver metastases of colorectal cancer (CRC) cells. The present study has investigated genes altered by hECM in CRC cells and particularly by heparan sulfate chains of hepatocyte proteoglycans. Gene profiling analysis shows that after 2xa0days on hECM, 226 genes are up-regulated more than 2-fold in strongly metastatic SM cells, including genes involved in growth arrest and apoptosis, signal transduction, cell migration, proliferation, communication and angiogenesis, with activation of the erbB signaling network and p53 effectors. Genes down-regulated by hECM include genes involved in lipogenesis and the S phase of the cell cycle. Further studies exploring the kinetics of gene expression after 4 and 7xa0days culture on hECM show induction of EGF family members and of stem cell markers. In particular, hECM, but not collagen, increases mRNA expression of HB-EGF and colon stem cell marker leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5). Expression of these genes is not induced by hECM depleted of the heparan sulfate chains of proteoglycans. Lastly, a specific cell population positive for cancer stem cell (CSC) markers LGR5, epCAM and CD133, but negative for CD44, appears after 7xa0days culture on hECM, a population which is reduced by 50xa0% in cells grown on heparan sulfated-depleted hECM. Collectively, the data suggest that hECM induces growth factors and receptors regulating proliferation of metastatic CRC in the liver and offers a growth advantage for specific populations expressing CSC markers.

P283 SORTILIN DEFICIENCY IMPROVES HEPATIC AND ADIPOSE TISSUE INSULIN RESISTANCE AND INFLAMMATION IN DIET-INDUCED OBESITY

Background and Aims: Sortilin is a trafficking molecule directing newly synthesized molecules from the trans-Golgi network to secretory pathways, endosomes, lysosomes or cell surface. Several of the molecules trafficked by sortilin, such as acidic sphingomyelinase (ASM) and sphingolipid activating proteins (SAPs), regulate the synthesis of ceramide, a major modulator of insulin signaling. We hypothesized that in sortilin mice, reduced hepatic ASM may improve insulin sensitivity and reduce steatosis in a diet-induced obesity (DIO) model. Methods: DIO and insulin resistance were induced by feeding high fat diet for 10 weeks to WT and sortilin mice. Results: Sortilin mice had significantly reduced body weight and visceral fat, despite similar food intake. Sortilin mice had better insulin tolerance test and displayed increased insulin signaling in both liver and adipose tissue as demonstrated by increased Akt phosphorylation. In accordance with the proposed role of sortilin in ASM trafficking, ASM activity in both liver and adipose tissue of sortilin mice was significantly reduced. Sortilin mice had almost no steatosis and a three-fold reduction in total hepatic triglyceride levels compared to WT mice. In addition, expression of proinflammatory cytokines was reduce in both livers and adipose tissue of sortilin. Looking at ceramide synthesis enzymes, we observed a significant reduction in ceramide synthase 6, which synthesizes long chain ceramides, in both liver and adipose tissue of sortilin. Conclusions: Sortilin deficiency induces a beneficial metabolic phenotype in DIO, with respect to both liver and adipose tissue, which may be mediated in part by reduced ASM activity and reduced ceramide levels.

Discriminatory metabolic and inflammatory parameters in serum and omental adipose tissue of obese patients with different insulin sensitivity

Objective Metabolically healthy obese phenotype is defined by high insulin sensitivity and lack of metabolic syndrome, parameters regulated by omental adipose tissue inflammation, ectopic fat deposition and adipose tissue dysfunction. Our study aimed to identify novel metabolic and inflammatory markers in serum and omental adipose tissue which characterize the “unhealthy” obese patients and distinguish them from obese patients with better metabolic profile. Design Cross-sectional study. Patients Subjects included 75 obese patients undergoing bariatric surgery at the Tel-Aviv Medical Center (mean age 43.9 ± 13.9, mean BMI 41 ± 8.4). The HOMA median value was used as a cut-off to differentiate between patients with better or worse insulin resistance. Measurements Demographic data, fasting serum insulin, glucose, bile acids, serum metabolic and inflammatory markers were obtained. During the bariatric surgery, omental adipose tissue was harvested and analyzed for metabolic and inflammatory markers using qRT-PCR. Logistic regressions were used to calculate odds ratio and 95% confidence interval for the prediction of the metabolic profile. Results Serum markers that were significantly higher among the obese with HOMA >6 were total bile acids. In the omental adipose tissue the inflammatory markers TNFα and ADAM17 were significantly higher among obese patients with HOMA >6. In multivariate analysis, the strongest predictor for insulin resistance was ADAM17 (OR = 1.82, 1.06–3.14, P = 0.031). Conclusions The study highlighted the predictive value of serum bile acids in identifying obese patients at high risk. Secondly, omental adipose tissue ADAM17 was revealed as a novel and strongest independent predictor for higher insulin resistance in morbidly obese patients.

963 SORTILIN-DEFICIENT HEPATOCYTES ARE LESS SUSCEPTIBLE TO BILE ACIDS-INDUCED INFLAMMATION AND APOPTOSIS

Background and Aims: Sortilin is a trafficking molecule directing newly synthesized molecules from the trans-Golgi network to secretory pathways or cell surface. One of the molecules trafficked by sortilin is acidic sphingomyelinase (ASMase), whose product ceramide participates in apoptosis signaling. We hypothesized due to less production of ceramide during liver injury, hepatocytes from sortilin−/− mice would be less sensitive to apoptosis. We have investigated liver injury, apoptosis and necrosis, inflammation and fibrosis in a bile duct ligation model in wild type (WT) and sortilin−/− mice. Methods: We have assessed liver damage and fibrosis 7 days after BDL using WT and sortilin−/− mice. The effect of bile acids on hepatocyte apoptosis and expression of inflammatory cytokines was determined in vitro in primary hepatocytes from WT and sortilin−/− mice. Results: Sortilin−/− mice displayed reduced liver damage compared to WT mice, as determined by lower serum AST, ALT, alkaline phosphatase and bilirubin. Sortilin−/− mice also had fewer areas of hepatocyte necrosis that result from bile infarcts, reduced hepatocyte apoptosis compared to WT mice, as well as reduced mRNA levels of collagen I. We determined the in vitro effect of bile acids on hepatocyte apoptosis and expression of proinflammatory cytokines and observed strong reduction of apoptosis and inflammatory cytokines in sortilin-deficient hepatocytes. Conclusion: Sortilin−/− mice have attenuated fibrosis and liver damage after BDL, due in part to reduced hepatocyte apoptosis and reduced inflammatory cytokines.

357 DIPEPTIDYL PEPTIDASE 4-DEFICIENT RATS ARE PROTECTED FROM HIGH FAT DIET-INDUCED CHOLESTATIC INJURY

357 DIPEPTIDYL PEPTIDASE 4-DEFICIENT RATS ARE PROTECTED FROM HIGH FAT DIET-INDUCED CHOLESTATIC INJURY I. Zvibel, S. Ben Shlomo, L. Rabinowich, I. Goldiner, E.M. Santo, Z. Halpern, R. Oren, S. Fishman. Gastroenterology, Internal Medicine D, Tel Aviv Sourasky Medical Center, Tel Aviv University, Tel Aviv, Gastroenterology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel E-mail: isab@tasmc.health.gov.il