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- Donati, Benedetta, et al.
(author)
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The rs2294918 E434K variant modulates PNPLA3 expression and liver damage.
- 2016
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In: Hepatology (Baltimore, Md.). - : Ovid Technologies (Wolters Kluwer Health). - 1527-3350 .- 0270-9139. ; 63:3, s. 787-798
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Journal article (peer-reviewed)abstract
- The PNPLA3 rs738409 polymorphism (I148M) is a major determinant of hepatic fat and predisposes to the full spectrum of liver damage in nonalcoholic fatty liver disease (NAFLD). Aim of this study was to evaluate whether additional PNPLA3 coding variants contribute to NAFLD susceptibility, first in individuals with contrasting phenotypes (with early onset NAFLD vs. very low aminotransferases), and then in a large validation cohort. Rare PNPLA3 variants were not detected by sequencing coding regions and intron-exon boundaries either in 142 patients with early-onset NAFLD, nor in 100 healthy individuals with ALT <22/20 IU/ml. Besides rs738409 I148M, the rs2294918 G>A polymorphism (E434K sequence variant) was over-represented in NAFLD (adjusted p=0.01). In 1447 subjects with and without NAFLD, the 148M-434E (p<0.0001), but not the 148M-434K haplotype (p>0.9), was associated with histological NAFLD and steatohepatitis. Both the I148M (p=0.0002) and E434K variants (p=0.044) were associated with serum ALT levels, by interacting each other, in that the 434K hampered the association with liver damage of the 148M allele (p=0.006). The E434K variant did not affect PNPLA3 enzymatic activity, but carriers of the rs2294918 A allele (434K) displayed lower hepatic PNPLA3 mRNA and protein levels (p<0.05).
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2. |
- Burza, Maria Antonella, 1980, et al.
(author)
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DEPDC5 variants increase fibrosis progression in Europeans with chronic HCV infection.
- 2016
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In: Hepatology (Baltimore, Md.). - : Ovid Technologies (Wolters Kluwer Health). - 1527-3350 .- 0270-9139. ; 63:2, s. 418-427
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Journal article (peer-reviewed)abstract
- Chronic hepatitis C virus (HCV) infection may progress to cirrhosis and hepatocellular carcinoma (HCC). Recently, two genetic variants, DEPDC5 rs1012068 and MICA rs2596542, were associated with the onset of HCC in Asian subjects with chronic HCV infection. The aim of the present study was to analyze whether DEPDC5 and MICA genetic variants were associated with liver disease progression in Europeans with chronic HCV infection. In a Northern Italian discovery cohort (n=477), neither DEPDC5 rs1012068 nor MICA rs2596542 were associated with HCC (n=150). However, DEPDC5 rs1012068 was independently associated with cirrhosis (n=300; p=0.049). The association of rs1012068 with moderate-severe fibrosis was confirmed in an independent cross-sectional German cohort (n=415; p=0.006). Furthermore, DEPDC5 rs1012068 predicted faster fibrosis progression in a prospective cohort (n=247; p=0.027). Next, we examined the distribution of non-synonymous DEPDC5 variants in the overall cross-sectional cohort (n=912). The presence of at least one variant increased the risk of moderate/severe fibrosis by 54% (p=0.040). To understand the molecular mechanism underlying the genetic association of DEPDC5 variants with fibrosis progression, we performed in vitro studies on immortalized hepatic stellate cells (LX-2). In these cells, down-regulation of DEPDC5 resulted in increased expression of β-catenin and production of its target matrix metallopeptidase 2 (MMP2), a secreted enzyme involved in fibrosis progression.
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3. |
- Mancina, Rosellina Margherita, et al.
(author)
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The MBOAT7-TMC4 Variant rs641738 Increases Risk of Nonalcoholic Fatty Liver Disease in Individuals of European Descent.
- 2016
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In: Gastroenterology. - : Elsevier BV. - 1528-0012 .- 0016-5085. ; 150:5, s. 1219-1230
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Journal article (peer-reviewed)abstract
- Nonalcoholic fatty liver disease (NAFLD) is a leading cause of liver damage and is characterized by steatosis. Genetic factors increase risk for progressive NAFLD. A genome-wide association study showed that the rs641738 C>T variant in the locus that contains the membrane bound O-acyltransferase domain-containing 7 gene (MBOAT7, also called LPIAT1) and transmembrane channel-like 4 gene (TMC4) increased the risk for cirrhosis in alcohol abusers. We investigated whether the MBOAT7-TMC4 is a susceptibility locus for the development and progression of NAFLD.
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5. |
- Pingitore, Piero, 1986, et al.
(author)
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PNPLA3 overexpression results in reduction of proteins predisposing to fibrosis.
- 2016
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In: Human molecular genetics. - : Oxford University Press (OUP). - 1460-2083 .- 0964-6906. ; 25:23, s. 5212-5222
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Journal article (peer-reviewed)abstract
- Liver fibrosis is a pathological scarring response to chronic hepatocellular injury and hepatic stellate cells (HSCs) are key players in this process. PNPLA3 I148M is a common variant robustly associated with liver fibrosis but the mechanisms underlying this association are unknown.We aimed to examine a) the effect of fibrogenic and proliferative stimuli on PNPLA3 levels in HSCs and b) the role of wild type and mutant PNPLA3 overexpression on markers of HSC activation and fibrosis.Here we show that PNPLA3 is upregulated by the fibrogenic cytokine transforming growth factor-beta (TGF-β), but not by platelet-derived growth factor (PDGF), and is involved in the TGF-β-induced reduction in lipid droplets in primary human HSCs. Furthermore, we show that retinol release from human HSCs ex vivo is lower in cells with the loss-of-function PNPLA3 148M compared with 148I wild type protein. Stable overexpression of PNPLA3 148I wild type, but not 148M mutant, in human HSCs (LX-2 cells) induces a reduction in the secretion of matrix metallopeptidase 2 (MMP2), tissue inhibitor of metalloproteinase 1 and 2 (TIMP1 and TIMP2), which is mediated by retinoid metabolism.In conclusion, we show a role for PNPLA3 in HSC activation in response to fibrogenic stimuli. Moreover, we provide evidence to indicate that PNPLA3-mediated retinol release may protect against liver fibrosis by inducing a specific signature of proteins involved in extracellular matrix remodeling.
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