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Luca Valenti - One of the best experts on this subject based on the ideXlab platform.

  • pnpla3 has retinyl palmitate lipase activity in human hepatic stellate cells
    Human Molecular Genetics, 2014
    Co-Authors: Carlo Pirazzi, Rosellina Margherita Mancina, Benedetta Maria Motta, Maria Antonella Burza, Yvelise Ferro, Cesare Indiveri, Piero Pingitore, Kristina Hedfalk, Luca Valenti, Tiziana Montalcini
    Abstract:

    Retinoids are micronutrients that are stored as retinyl esters in the retina and hepatic stellate cells (HSCs). HSCs are key players in fibrogenesis in chronic liver diseases. The enzyme responsible for hydrolysis and release of retinyl esters from HSCs is unknown and the relationship between retinoid metabolism and liver disease remains unclear. We hypothesize that the Patatin-Like Phospholipase domain-containing 3 (PNPLA3) protein is involved in retinol metabolism in HSCs. We tested our hypothesis both in primary human HSCs and in a human cohort of subjects with non-alcoholic fatty liver disease (N = 146). Here we show that PNPLA3 is highly expressed in human HSCs. Its expression is regulated by retinol availability and insulin, and increased PNPLA3 expression results in reduced lipid droplet content. PNPLA3 promotes extracellular release of retinol from HSCs in response to insulin. We also show that purified wild-type PNPLA3 hydrolyzes retinyl palmitate into retinol and palmitic acid. Conversely, this enzymatic activity is markedly reduced with purified PNPLA3 148M, a common mutation robustly associated with liver fibrosis and hepatocellular carcinoma development. We also find the PNPLA3 I148M genotype to be an independent (P = 0.009 in a multivariate analysis) determinant of circulating retinol-binding protein 4, a reliable proxy for retinol levels in humans. This study identifies PNPLA3 as a lipase responsible for retinyl-palmitate hydrolysis in HSCs in humans. Importantly, this indicates a potential novel link between HSCs, retinoid metabolism and PNPLA3 in determining the susceptibility to chronic liver disease.

  • pnpla3 i148m polymorphism and progressive liver disease
    World Journal of Gastroenterology, 2013
    Co-Authors: Paola Dongiovanni, Rosellina Margherita Mancina, Stefano Romeo, Benedetta Donati, Roberta Fares, Rosa Lombardi, Luca Valenti
    Abstract:

    The 148 Isoleucine to Methionine protein variant (I148M) of Patatin-Like Phospholipase domain-containing 3 (PNPLA3), a protein is expressed in the liver and is involved in lipid metabolism, has recently been identified as a major determinant of liver fat content. Several studies confirmed that the I148M variant predisposes towards the full spectrum of liver damage associated with fatty liver: from simple steatosis to steatohepatitis and progressive fibrosis. Furthermore, the I148M variant represents a major determinant of progression of alcohol related steatohepatitis to cirrhosis, and to influence fibrogenesis and related clinical outcomes in chronic hepatitis C virus hepatitis, and possibly chronic hepatitis B virus hepatitis, hereditary hemochromatosis and primary sclerosing cholangitis. All in all, studies suggest that the I148M polymorphism may represent a general modifier of fibrogenesis in liver diseases. Remarkably, the effect of the I148M variant on fibrosis was independent of that on hepatic steatosis and inflammation, suggesting that it may affect both the quantity and quality of hepatic lipids and the biology of non-parenchymal liver cells besides hepatocytes, directly promoting fibrogenesis. Therefore, PNPLA3 is a key player in liver disease progression. Assessment of the I148M polymorphism will possibly inform clinical practice in the future, whereas the determination of the effect of the 148M variant will reveal mechanisms involved in hepatic fibrogenesis.

  • the i148m variant of pnpla3 reduces the response to docosahexaenoic acid in children with non alcoholic fatty liver disease
    Journal of Medicinal Food, 2013
    Co-Authors: Valerio Nobili, Anna Alisi, Benedetta Donati, Giorgio Bedogni, Luca Valenti
    Abstract:

    Abstract The aim of this secondary analysis of a randomized controlled trial was to test whether the I148M variant of Patatin-Like Phospholipase domain-containing protein-3 (PNPLA3) is associated with the response to docosahexaenoic acid (DHA) in children with non-alcoholic fatty liver disease (NAFLD). Sixty children with NAFLD were randomized in equal numbers to DHA 250 mg/day, DHA 500 mg/day or placebo. Coherently with the primary analysis, the probability of more severe steatosis after 24 months of DHA supplementation was 50% lower [95% confidence interval (CI) −59% to −42%)] in the combined DHA 250 and 500 mg/day groups versus placebo. The present secondary analysis revealed an independent effect of PNPLA3 status on the response to DHA. In fact, the probability of more severe steatosis was higher (37%, 95% CI 26–48%) for the PNPLA3 M/M versus I/M genotype and lower (−12%, 95% CI −21% to −3%) for the I/I versus I/M genotype (Somers' D for repeated measures). We conclude that the 148M allele of PNPLA3 i...

  • patatin like Phospholipase domain containing 3 i148m affects liver steatosis in patients with chronic hepatitis b
    Hepatology, 2013
    Co-Authors: M Vigano, Benedetta Maria Motta, Paola Dongiovanni, Luca Valenti, Benedetta Donati, P Lampertico, F Facchetti, Roberta Dambrosio, Solange Romagnoli, S Fargion
    Abstract:

    Steatosis is a common histopathological feature of chronic hepatitis B (CHB) and has been associated with severity of liver disease. Recently, the rs738409 I148M Patatin-Like Phospholipase domain-containing 3 (PNPLA3) polymorphism has been demonstrated to influence steatosis susceptibility and fibrosis progression in patients with different liver diseases, but no data are yet available for CHB. The aim of this study was to evaluate whether PNPLA3 I148M influences steatosis susceptibility in a large series of patients with CHB. We enrolled 235 treatment-naive CHB patients consecutively examined by percutaneous liver biopsy. In ≥2-cm-long liver tissue cores, steatosis and fibrosis were staged by Kleiner and METAVIR scores, respectively. The I148M polymorphism was determined by Taqman assays. Steatosis was present in 146 (62%) patients, of whom 24 (10%) had severe (>33% of hepatocytes) steatosis. Steatosis was independently associated with age (odds ratio [OR]: 2.67; confidence interval [CI]: 1.50-4.92; for age ≥50 years), body mass index (BMI; OR, 2.84; CI, 1.30-6.76; for BMI ≥27.5 kg/m2), diabetes or impaired fasting glucose (OR, 4.45; CI, 1.10-30.0), and PNPLA3 148M allele (OR, 1.62; CI, 1.00-7.00; for each 148M allele). Independent predictors of severe steatosis were BMI (OR, 3.60; CI, 1.39-9.22; for BMI ≥27.5 kg/m2) and PNPLA3 148M allele (OR, 6.03; CI, 1.23-5.0; for each 148M allele). PNPLA3 148M alleles were associated with a progressive increase in severe steatosis in patients with acquired cofactors, such severe overweight and a history of alcohol intake (P = 0.005). Conclusion: In CHB patients, the PNPLA3 I148M polymorphism influences susceptibility to steatosis and, in particular, when associated with severe overweight and alcohol intake, severe steatosis. (Hepatology 2013;58:1245–1252)

  • pnpla3 i148m variant and hepatocellular carcinoma a common genetic variant for a rare disease
    Digestive and Liver Disease, 2013
    Co-Authors: Luca Valenti, Maria Antonella Burza, Paola Dongiovanni, Stefano Ginanni Corradini, Stefano Romeo
    Abstract:

    Abstract Hepatocellular carcinoma (HCC) is highly associated with chronic liver disease. The rs738409 genetic variant in the Patatin-Like Phospholipase domain-containing 3 ( PNPLA3 , adiponutrin) gene has been implicated as a genetic determinant of the entire spectrum of liver diseases, ranging from steatosis, chronic hepatitis, cirrhosis and ultimately to HCC. In this review, first we will examine the current genetic theories of disease susceptibility. Next, we will analyze the evidences for the association between PNPLA3 I148M variant and HCC. Moreover, we will exploit this association to propose a new paradigm in human genetics: a common genetic variant contributing to a rare disease. Finally, we will examine the molecular genetics of PNPLA3 and, specifically, the theories that have been proposed to explain the function of PNPLA3 in health and disease.

Stefano Romeo - One of the best experts on this subject based on the ideXlab platform.

  • the role of pnpla3 in health and disease
    Biochimica et Biophysica Acta, 2019
    Co-Authors: Piero Pingitore, Stefano Romeo
    Abstract:

    Abstract The human Patatin-Like Phospholipase domain-containing 3 (PNPLA3) gene encodes for a protein of 481 amino-acids. The variant rs738409 is a cytosine to guanine substitution, encoding for the isoleucine to methionine substitution at position 148 (I148M) of the protein. This variant is strongly associated with the entire spectrum of liver disease. Although this variant is one of the best characterized and deeply studied, the mechanism behind the PNPLA3 and the liver disease is still not well defined. Functionally, it has become clear that the PNPLA3 protein is an enzyme with lipase activity towards triglycerides and retinyl esters, and acyltransferase activity on phospholipids. The aim of this review is to collect the latest data, obtained by in vitro and in vivo experiments, on the functional aspects of the PNPLA3 protein. Defining the precise role of PNPLA3 in the liver lipid metabolism, in order to develop novel therapies for the treatment of liver disease, will be the key of future research.

  • Lipase tug of war: PNPLA3 sequesters ABHD5 from ATGL.
    Nature metabolism, 2019
    Co-Authors: Stefano Romeo, David B. Savage
    Abstract:

    A common missense variant (I148M) in Patatin-Like Phospholipase domain-containing protein 3 (PNPLA3) was strongly linked to human fatty liver disease in 2008, but the underlying mechanisms have since remained unclear. Compelling data from Yang et al., published in Nature Metabolism, suggest that PNPLA3 binds ABHD5, sequestering it and preventing it from activating ATGL, the major intracellular triglyceride lipase.

  • pnpla3 gene in liver diseases
    Journal of Hepatology, 2016
    Co-Authors: Stefano Romeo, Eric Trepo, Jessica Zucmanrossi, Pierre Nahon
    Abstract:

    Genome-wide association studies (GWAS) in the field of liver diseases have revealed previously unknown pathogenic loci and generated new biological hypotheses. In 2008, a GWAS performed in a population-based sample study, where hepatic liver fat content was measured by magnetic spectroscopy, showed a strong association between a variant (rs738409 C>G p.I148M) in the Patatin-Like Phospholipase domain containing 3 (PNPLA3) gene and nonalcoholic fatty liver disease. Further replication studies have shown robust associations between PNPLA3 and steatosis, fibrosis/cirrhosis, and hepatocellular carcinoma on a background of metabolic, alcoholic, and viral insults. The PNPLA3 protein has lipase activity towards triglycerides in hepatocytes and retinyl esters in hepatic stellate cells. The I148M substitution leads to a loss of function promoting triglyceride accumulation in hepatocytes. Although PNPLA3 function has been extensively studied, the molecular mechanisms leading to hepatic fibrosis and carcinogenesis remain unclear. This unsuspected association has highlighted the fact that liver fat metabolism may have a major impact on the pathophysiology of liver diseases. Conversely, alone, this locus may have limited predictive value with regard to liver disease outcomes in clinical practice. Additional studies at the genome-wide level will be required to identify new variants associated with liver damage and cancer to explain a greater proportion of the heritability of these phenotypes. Thus, incorporating PNPLA3 and other genetic variants in combination with clinical data will allow for the development of tailored predictive models. This attractive approach should be evaluated in prospective cohorts.

  • the pnpla3 ile148met interacts with overweight and dietary intakes on fasting triglyceride levels
    Genes and Nutrition, 2014
    Co-Authors: Ivana A Stojkovic, Stefano Romeo, Ulrika Ericson, Gull Rukh, Martin Riddestrale, Marju Orhomelander
    Abstract:

    The Ile148Met (rs738409, G-allele) in the Patatin-Like Phospholipase domain-containing protein 3 gene (PNPLA3) associates with liver fat content and may lead to loss-of-function (hydrolysis) or gain-of-function (CoA-dependent lysophosphatidic acid acyltransferase) defects. PNPLA3 is up-regulated by dietary carbohydrates, and interactions between rs738409 and carbohydrates, and sugar and ω6:ω3-polyunsaturated fatty acid (PUFA) ratio on hepatic fat accumulation have been reported. We examined interaction between rs738409 and overweight, and between rs738409 and dietary intakes (carbohydrates, sucrose and ω6:ω3-PUFA ratio), on fasting triglyceride levels. From the Malmo Diet and Cancer Study-Cardiovascular Cohort, 4,827 individuals without diabetes aged 58 ± 6 years, 2,346 with BMI ≤ 25 kg/m2 and 2,478 with BMI > 25 kg/m2, were included in cross-sectional analyses. Dietary data were collected by a modified diet history method. Overweight modified the association between rs738409 and fasting triglyceride levels (P interaction = 0.003). G-allele associated with lower triglycerides only among overweight individuals (P = 0.01). Nominally, significant interaction on triglyceride levels was observed between rs738409 and sucrose among normal-weight individuals (P interaction = 0.03). G-allele associated with lower triglycerides among overweight individuals in the lowest tertiles of carbohydrate and ω6:ω3-PUFA ratio (P = 0.04 and P = 0.001) and with higher triglycerides among normal-weight individuals in the highest tertile of sucrose (P = 0.001). We conclude that overweight and dietary sucrose may modify the association between rs738409 and fasting triglyceride levels.

  • pnpla3 i148m polymorphism and progressive liver disease
    World Journal of Gastroenterology, 2013
    Co-Authors: Paola Dongiovanni, Rosellina Margherita Mancina, Stefano Romeo, Benedetta Donati, Roberta Fares, Rosa Lombardi, Luca Valenti
    Abstract:

    The 148 Isoleucine to Methionine protein variant (I148M) of Patatin-Like Phospholipase domain-containing 3 (PNPLA3), a protein is expressed in the liver and is involved in lipid metabolism, has recently been identified as a major determinant of liver fat content. Several studies confirmed that the I148M variant predisposes towards the full spectrum of liver damage associated with fatty liver: from simple steatosis to steatohepatitis and progressive fibrosis. Furthermore, the I148M variant represents a major determinant of progression of alcohol related steatohepatitis to cirrhosis, and to influence fibrogenesis and related clinical outcomes in chronic hepatitis C virus hepatitis, and possibly chronic hepatitis B virus hepatitis, hereditary hemochromatosis and primary sclerosing cholangitis. All in all, studies suggest that the I148M polymorphism may represent a general modifier of fibrogenesis in liver diseases. Remarkably, the effect of the I148M variant on fibrosis was independent of that on hepatic steatosis and inflammation, suggesting that it may affect both the quantity and quality of hepatic lipids and the biology of non-parenchymal liver cells besides hepatocytes, directly promoting fibrogenesis. Therefore, PNPLA3 is a key player in liver disease progression. Assessment of the I148M polymorphism will possibly inform clinical practice in the future, whereas the determination of the effect of the 148M variant will reveal mechanisms involved in hepatic fibrogenesis.

Helen H Hobbs - One of the best experts on this subject based on the ideXlab platform.

  • accumulation of pnpla3 on lipid droplets is the basis of associated hepatic steatosis
    Proceedings of the National Academy of Sciences of the United States of America, 2019
    Co-Authors: Soumik Basuray, Eriks Smagris, Jonathan C Cohen, Helen H Hobbs, Yang Wang
    Abstract:

    Fatty liver disease (FLD) is a disorder in which accumulation of triglycerides (TGs) in the liver can lead to inflammation, fibrosis, and cirrhosis. Previously, we identified a variant (I148M) in Patatin-Like Phospholipase domain-containing protein 3 (PNPLA3) that is strongly associated with FLD, but the mechanistic basis for the association remains elusive. Although PNPLA3 has TG hydrolase activity in vitro, inactivation or overexpression of the WT protein in mice does not cause steatosis. In contrast, expression of two catalytically defective forms of PNPLA3 (I148M or S47A) in sucrose-fed mice causes accumulation of both PNPLA3 and TGs on hepatic lipid droplets (LDs). To determine if amassing PNPLA3 on LDs is a cause or consequence of steatosis, we engineered a synthetic isoform of PNPLA3 that uncouples protein accumulation from loss of enzymatic activity. Expression of a ubiquitylation-resistant form of PNPLA3 in mice caused accumulation of PNPLA3 on hepatic LDs and development of FLD. Lowering PNPLA3 levels by either shRNA knockdown or proteolysis-targeting chimera (PROTAC)-mediated degradation reduced liver TG content in mice overexpressing PNPLA3(148M). Taken together, our results show that the steatosis associated with PNPLA3(148M) is caused by accumulation of PNPLA3 on LDs.

  • the pnpla3 variant associated with fatty liver disease i148m accumulates on lipid droplets by evading ubiquitylation
    Hepatology, 2017
    Co-Authors: Soumik Basuray, Eriks Smagris, Jonathan C Cohen, Helen H Hobbs
    Abstract:

    A sequence variation (I148M) in Patatin-Like Phospholipase domain-containing protein 3 (PNPLA3) is strongly associated with fatty liver disease (FLD), but the underlying mechanism remains obscure. Here we used knock-in (KI) mice (Pnpla3148M/M) to examine the mechanism responsible for accumulation of triglyceride (TG) and PNPLA3 in hepatic lipid droplets (LDs). No differences were found between Pnpla3148M/M and Pnpla3+/+ mice in hepatic TG synthesis, utilization, or secretion. These results are consistent with TG accumulation in the Pnpla3148M/M mice being caused by impaired TG mobilization from LDs. Sucrose feeding, which is required to elicit fatty liver in KI mice, led to a much larger and more persistent increase in PNPLA3 protein in the KI than in the WT mice. Inhibition of the proteasome (bortezomib), but not macroautophagy (3-methyladenine), markedly increased PNPLA3 levels in WT mice, coincident with the appearance of ubiquitylated forms of the protein. Bortezomib did not increase PNPLA3 levels in Pnpla3148M/M mice, and only trace amounts of ubiquitylated PNPLA3 were seen in these animals. Conclusion: These results are consistent with the notion that the 148M variant disrupts ubiquitylation and proteasomal degradation of PNPLA3, resulting in accumulation of PNPLA3-148M and impaired mobilization of TG from LDs. This article is protected by copyright. All rights reserved.

  • expression and characterization of a pnpla3 protein isoform i148m associated with nonalcoholic fatty liver disease
    Journal of Biological Chemistry, 2011
    Co-Authors: Yongcheng Huang, Jonathan C Cohen, Helen H Hobbs
    Abstract:

    A genetic variant of PNPLA3 (Patatin-Like Phospholipase domain-containing 3; PNPLA3-I148M), a serine protease of unknown function, is associated with accumulation of triacylglycerol (TAG) in the liver. To determine the biological substrates of PNPLA3 and the effect of the I148M substitution on enzymatic activity and substrate specificity, we purified and characterized recombinant human PNPLA3 and PNPLA3-I148M. Maximal hydrolytic activity of PNPLA3 was observed against the three major glycerolipids, TAG, diacylglycerol, and monoacylglycerol, with a strong preference for oleic acid as the acyl moiety. Substitution of methionine for isoleucine at position 148 markedly decreased the Vmax of the enzyme for glycerolipids but had only a modest effect on the Km. Purified PNPLA3 also catalyzed the hydrolysis of oleoyl-CoA, but the Vmax was 100-fold lower for oleoyl-CoA than for triolein. The thioesterase activity required the catalytic serine but was only modestly decreased by the I148M substitution. The enzyme had little or no hydrolytic activity against the other lipid substrates tested, including phospholipids, cholesteryl ester, and retinyl esters. Neither the wild-type nor mutant enzyme catalyzed transfer of oleic acid from oleoyl-CoA to glycerophosphate, lysophosphatidic acid, or diacylglycerol, suggesting that the enzyme does not promote de novo TAG synthesis. Taken together, our results are consistent with the notion that PNPLA3 plays a role in the hydrolysis of glycerolipids and that the I148M substitution causes a loss of function, although we cannot exclude the possibility that the enzyme has additional substrates or activities.

  • a feed forward loop amplifies nutritional regulation of pnpla3
    Proceedings of the National Academy of Sciences of the United States of America, 2010
    Co-Authors: Yongcheng Huang, John Zhong Li, Jonathan C Cohen, Shaoqing He, Timothy F Osborne, Helen H Hobbs
    Abstract:

    The upsurge in prevalence of obesity has spawned an epidemic of nonalcoholic fatty liver disease (NAFLD). Previously, we identified a sequence variant (I148M) in Patatin-Like Phospholipase domain-containing protein 3 (PNPLA3) that confers susceptibility to both hepatic triglyceride (TG) deposition and liver injury. To glean insights into the biological role of PNPLA3, we examined the molecular mechanisms by which nutrient status controls hepatic expression of PNPLA3. PNPLA3 mRNA levels, which were low in fasting animals, increased ∼90-fold with carbohydrate feeding. The increase was mimicked by treatment with a liver X receptor (LXR) agonist and required the transcription factor SREBP-1c. The site of SREBP-1c binding was mapped to intron 1 of Pnpla3 using chromatin immunoprecipitation and electrophoretic mobility shift assays. SREBP-1c also promotes fatty acid synthesis by activating several genes encoding enzymes in the biosynthetic pathway. Addition of fatty acids (C16:0, C18:1, and C18:2) to the medium of cultured hepatocytes (HuH-7) increased PNPLA3 protein mass without altering mRNA levels. The posttranslational increase in PNPLA3 levels persisted after blocking TG synthesis with triascin C. Oleate (400 μM) treatment prolonged the half-life of PNPLA3 from 2.4 to 6.7 h. These findings are consistent with nutritional control of PNPLA3 being effected by a feed-forward loop; SREBP-1c promotes accumulation of PNPLA3 directly by activating Pnpla3 transcription and indirectly by inhibiting PNPLA3 degradation through the stimulation of fatty acid synthesis.

  • a sequence variation i148m in pnpla3 associated with nonalcoholic fatty liver disease disrupts triglyceride hydrolysis
    Journal of Biological Chemistry, 2010
    Co-Authors: Shaoqing He, John Zhong Li, Jonathan C Cohen, Christopher Mcphaul, Rita Garuti, Lisa N Kinch, Nick V Grishin, Helen H Hobbs
    Abstract:

    Abstract Obesity and insulin resistance are associated with deposition of triglycerides in tissues other than adipose tissue. Previously, we showed that a missense mutation (I148M) in PNPLA3 (Patatin-Like Phospholipase domain-containing 3 protein) is associated with increased hepatic triglyceride content in humans. Here we examined the effect of the I148M substitution on the enzymatic activity and cellular location of PNPLA3. Structural modeling predicted that the substitution of methionine for isoleucine at residue 148 would restrict access of substrate to the catalytic serine at residue 47. In vitro assays using recombinant PNPLA3 partially purified from Sf9 cells confirmed that the wild type enzyme hydrolyzes emulsified triglyceride and that the I148M substitution abolishes this activity. Expression of PNPLA3-I148M, but not wild type PNPLA3, in cultured hepatocytes or in the livers of mice increased cellular triglyceride content. Cell fractionation studies revealed that ∼90% of wild type PNPLA3 partitioned between membranes and lipid droplets; substitution of isoleucine for methionine at position 148 did not alter the subcellular distribution of the protein. These data are consistent with PNPLA3-I148M promoting triglyceride accumulation by limiting triglyceride hydrolysis.

Paola Dongiovanni - One of the best experts on this subject based on the ideXlab platform.

  • pnpla3 i148m polymorphism and progressive liver disease
    World Journal of Gastroenterology, 2013
    Co-Authors: Paola Dongiovanni, Rosellina Margherita Mancina, Stefano Romeo, Benedetta Donati, Roberta Fares, Rosa Lombardi, Luca Valenti
    Abstract:

    The 148 Isoleucine to Methionine protein variant (I148M) of Patatin-Like Phospholipase domain-containing 3 (PNPLA3), a protein is expressed in the liver and is involved in lipid metabolism, has recently been identified as a major determinant of liver fat content. Several studies confirmed that the I148M variant predisposes towards the full spectrum of liver damage associated with fatty liver: from simple steatosis to steatohepatitis and progressive fibrosis. Furthermore, the I148M variant represents a major determinant of progression of alcohol related steatohepatitis to cirrhosis, and to influence fibrogenesis and related clinical outcomes in chronic hepatitis C virus hepatitis, and possibly chronic hepatitis B virus hepatitis, hereditary hemochromatosis and primary sclerosing cholangitis. All in all, studies suggest that the I148M polymorphism may represent a general modifier of fibrogenesis in liver diseases. Remarkably, the effect of the I148M variant on fibrosis was independent of that on hepatic steatosis and inflammation, suggesting that it may affect both the quantity and quality of hepatic lipids and the biology of non-parenchymal liver cells besides hepatocytes, directly promoting fibrogenesis. Therefore, PNPLA3 is a key player in liver disease progression. Assessment of the I148M polymorphism will possibly inform clinical practice in the future, whereas the determination of the effect of the 148M variant will reveal mechanisms involved in hepatic fibrogenesis.

  • patatin like Phospholipase domain containing 3 i148m affects liver steatosis in patients with chronic hepatitis b
    Hepatology, 2013
    Co-Authors: M Vigano, Benedetta Maria Motta, Paola Dongiovanni, Luca Valenti, Benedetta Donati, P Lampertico, F Facchetti, Roberta Dambrosio, Solange Romagnoli, S Fargion
    Abstract:

    Steatosis is a common histopathological feature of chronic hepatitis B (CHB) and has been associated with severity of liver disease. Recently, the rs738409 I148M Patatin-Like Phospholipase domain-containing 3 (PNPLA3) polymorphism has been demonstrated to influence steatosis susceptibility and fibrosis progression in patients with different liver diseases, but no data are yet available for CHB. The aim of this study was to evaluate whether PNPLA3 I148M influences steatosis susceptibility in a large series of patients with CHB. We enrolled 235 treatment-naive CHB patients consecutively examined by percutaneous liver biopsy. In ≥2-cm-long liver tissue cores, steatosis and fibrosis were staged by Kleiner and METAVIR scores, respectively. The I148M polymorphism was determined by Taqman assays. Steatosis was present in 146 (62%) patients, of whom 24 (10%) had severe (>33% of hepatocytes) steatosis. Steatosis was independently associated with age (odds ratio [OR]: 2.67; confidence interval [CI]: 1.50-4.92; for age ≥50 years), body mass index (BMI; OR, 2.84; CI, 1.30-6.76; for BMI ≥27.5 kg/m2), diabetes or impaired fasting glucose (OR, 4.45; CI, 1.10-30.0), and PNPLA3 148M allele (OR, 1.62; CI, 1.00-7.00; for each 148M allele). Independent predictors of severe steatosis were BMI (OR, 3.60; CI, 1.39-9.22; for BMI ≥27.5 kg/m2) and PNPLA3 148M allele (OR, 6.03; CI, 1.23-5.0; for each 148M allele). PNPLA3 148M alleles were associated with a progressive increase in severe steatosis in patients with acquired cofactors, such severe overweight and a history of alcohol intake (P = 0.005). Conclusion: In CHB patients, the PNPLA3 I148M polymorphism influences susceptibility to steatosis and, in particular, when associated with severe overweight and alcohol intake, severe steatosis. (Hepatology 2013;58:1245–1252)

  • pnpla3 i148m variant and hepatocellular carcinoma a common genetic variant for a rare disease
    Digestive and Liver Disease, 2013
    Co-Authors: Luca Valenti, Maria Antonella Burza, Paola Dongiovanni, Stefano Ginanni Corradini, Stefano Romeo
    Abstract:

    Abstract Hepatocellular carcinoma (HCC) is highly associated with chronic liver disease. The rs738409 genetic variant in the Patatin-Like Phospholipase domain-containing 3 ( PNPLA3 , adiponutrin) gene has been implicated as a genetic determinant of the entire spectrum of liver diseases, ranging from steatosis, chronic hepatitis, cirrhosis and ultimately to HCC. In this review, first we will examine the current genetic theories of disease susceptibility. Next, we will analyze the evidences for the association between PNPLA3 I148M variant and HCC. Moreover, we will exploit this association to propose a new paradigm in human genetics: a common genetic variant contributing to a rare disease. Finally, we will examine the molecular genetics of PNPLA3 and, specifically, the theories that have been proposed to explain the function of PNPLA3 in health and disease.

  • patatin like Phospholipase domain containing 3 i148m polymorphism steatosis and liver damage in chronic hepatitis c
    Hepatology, 2011
    Co-Authors: Luca Valenti, Paola Dongiovanni, Maria Grazia Rumi, E Galmozzi, Alessio Aghemo, Enedetta Del Menico, Stella De Nicola, Marco Maggioni, Anna Ludovica Fracanzani, Raffaela Rametta
    Abstract:

    Steatosis has been reported to negatively influence the natural history of chronic hepatitis C (CHC), but controversy remains over its causal role due to the confounding effect of adiposity, insulin resistance, and diabetes. The rs738409 C>G Patatin-Like Phospholipase domain-containing 3 (PNPLA3) single nucleotide polymorphism (SNP), encoding for the I148M protein variant, influences liver fat without affecting insulin resistance and body composition. The aim of this study was to evaluate the effect of the rs738409 CG genotype on liver fat and fibrosis in CHC patients. We also explored the possible effect of PNPLA3 genotype on other steatosis-related complications, namely, treatment failure and hepatocellular carcinoma (HCC) development. To this end we considered two independent series of 325 and 494 CHC patients with available DNA and liver biopsy followed at tertiary referral centers in northern Italy. The rs738409 genotype was determined by a Taqman assay. The rs738409 GG genotype, observed in 10% of patients, was associated with steatosis independently of age, sex, body mass index (BMI), diabetes, alcohol intake, and viral genotype (odds ratio [OR] 1.90, 95% confidence interval [CI] 1.4-2.7; P < 0.001). The association with rs738409 genotype was confirmed for severe steatosis, was independent of alanine aminotransferase (ALT) and gamma-glutamyl transferase (GGT) values, and was observed in all viral genotypes but the 3. The rs738409 GG genotype was associated with fibrosis stage and cirrhosis (OR 1.47, 95% CI 1.2-1.9; P = 0.002), treatment response (n = 470; OR 0.63, 95% CI 0.4-0.8; P = 0.006), and HCC occurrence (n = 325; OR 2.16, 95% CI 1.3-3.6; P = 0.002), independently of confounders. Conclusion: The rs738409 PNPLA3 genotype influences steatosis development in CHC and is independently associated with cirrhosis and other steatosis-related clinical outcomes, such as lack of response to antiviral treatment and possibly HCC. (HEPATOLOGY 2011)

  • homozygosity for the patatin like Phospholipase 3 adiponutrin i148m polymorphism influences liver fibrosis in patients with nonalcoholic fatty liver disease
    Hepatology, 2010
    Co-Authors: Luca Valenti, Paola Dongiovanni, Valerio Nobili, E Galmozzi, Raffaela Rametta, Ahmad Alserri, Ann K Daly, Enrico Mozzi, G C Roviaro, Ester Vanni
    Abstract:

    Inherited factors play a major role in the predisposition to nonalcoholic fatty liver disease (NAFLD), and the rs738409 CG polymorphism of PNPLA3/adiponutrin, encoding for the isoleucine-to-methionine substitution at residue 148 (I148M) protein variant, has recently been recognized as a major determinant of liver fat content. However, the effect of the rs738409 polymorphism on the severity of liver fibrosis in patients with NAFLD is still unknown. In this study, we considered 253 Italian patients, 179 healthy controls, and 71 family trios with an affected child with NAFLD. Analyses were replicated in 321 patients from the United Kingdom. The rs738409 polymorphism was determined by TaqMan assays. Liver histology was scored according to Kleiner et al. Hepatic expression of genes regulating liver damage was assessed by real-time polymerase chain reaction in 52 patients. The rs738409 GG genotype was more prevalent in patients than in controls (14% versus 3%, adjusted odds ratio [OR] = 3.29, 95% confidence interval [CI] = 1.8-6.9), and in the family study, the G allele was overtransmitted to affected children (P = 0.001). In Italian and United Kingdom patients, adiponutrin genotype influenced alanine aminotransferase levels and the severity of steatosis. Adiponutrin genotype was associated with the expression of genes involved in the steatosis-related liver damage, including the proapoptotic molecule Fas ligand. In the whole series combined, adiponutrin genotype was associated with steatosis grade >1 (OR = 1.35, 95% CI = 1.04-1.76), nonalcoholic steatohepatitis (OR = 1.5, 95% CI = 1.12-2.04), and fibrosis stage >1 (OR = 1.5, 95% CI = 1.09-2.12), independent of age, body mass index, and diabetes. Adiponutrin genotype demonstrated a dose effect with heterozygote risk intermediate between CC and GG homozygotes. Conclusion: In patients with NAFLD, adiponutrin rs738409 CG genotype, encoding for I148M, is associated with the severity of steatosis and fibrosis and the presence of nonalcoholic steatohepatitis. (Hepatology 2010;51:1209–1217)

Teiji Sawa - One of the best experts on this subject based on the ideXlab platform.

  • Pseudomonas aeruginosa Type III Secretory Toxin ExoU and Its Predicted Homologs
    MDPI AG, 2016
    Co-Authors: Teiji Sawa, Saeko Hamaoka, Mao Kinoshita, Atsushi Kainuma, Yoshifumi Naito, Koichi Akiyama, Hideya Kato
    Abstract:

    Pseudomonas aeruginosa ExoU, a type III secretory toxin and major virulence factor with Patatin-Like Phospholipase activity, is responsible for acute lung injury and sepsis in immunocompromised patients. Through use of a recently updated bacterial genome database, protein sequences predicted to be homologous to Ps. aeruginosa ExoU were identified in 17 other Pseudomonas species (Ps. fluorescens, Ps. lundensis, Ps. weihenstephanensis, Ps. marginalis, Ps. rhodesiae, Ps. synxantha, Ps. libanensis, Ps. extremaustralis, Ps. veronii, Ps. simiae, Ps. trivialis, Ps. tolaasii, Ps. orientalis, Ps. taetrolens, Ps. syringae, Ps. viridiflava, and Ps. cannabina) and 8 Gram-negative bacteria from three other genera (Photorhabdus, Aeromonas, and Paludibacterium). In the alignment of the predicted primary amino acid sequences used for the phylogenetic analyses, both highly conserved and nonconserved parts of the toxin were discovered among the various species. Further comparative studies of the predicted ExoU homologs should provide us with more detailed information about the unique characteristics of the Ps. aeruginosa ExoU toxin

  • lysoPhospholipase a activity of pseudomonas aeruginosa type iii secretory toxin exou
    Biochemical and Biophysical Research Communications, 2004
    Co-Authors: Miki Tamura, Temitayo Ajayi, Leonard R Allmond, Kiyoshi Moriyama, Jeanine P Wienerkronish, Teiji Sawa
    Abstract:

    Acute lung injury in Pseudomonas aeruginosa pneumonia depends primarily on ExoU that is delivered directly into the eukaryotic cell via the type III secretion system. Recent studies demonstrated that ExoU has lipase activity, and that the cytotoxicity of ExoU is dependent on its Patatin-Like Phospholipase domain. We investigated the Phospholipase A (PLA) activity of ExoU. ExoU, but not non-catalytic ExoU- S142A , preincubated with the BEAS-2B cell lysate showed a weak increase of Ca 2+ -independent PLA 2 activity. When activated ExoU was mixed with secretory type PLA 2 , more Phospholipase activity was observed, suggesting that ExoU has lysoPhospholipase A (lysoPLA) activity. A significant increase in lysoPLA activity was also observed. Glycerol enhanced this activity and inhibitors of iPLA 2 suppressed ExoU’s lysoPLA activity. Our results suggest that ExoU has a potent lysoPLA activity that requires the presence of the catalytically active site Ser 142 with an unknown eukaryotic cell factor(s) for its activation.