Browsing by Subject "TM6SF2"

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  • Emdin, Connor A.; Haas, Mary E.; Khera, Amit V.; Aragam, Krishna; Chaffin, Mark; Klarin, Derek; Hindy, George; Jiang, Lan; Wei, Wei-Qi; Feng, Qiping; Karjalainen, Juha; Havulinna, Aki; Kiiskinen, Tuomo; Bick, Alexander; Ardissino, Diego; Wilson, James G.; Schunkert, Heribert; McPherson, Ruth; Watkins, Hugh; Elosua, Roberto; Bown, Matthew J.; Samani, Nilesh J.; Baber, Usman; Erdmann, Jeanette; Gupta, Namrata; Danesh, John; Saleheen, Danish; Chang, Kyong-Mi; Vujkovic, Marijana; Voight, Ben; Damrauer, Scott; Lynch, Julie; Kaplan, David; Serper, Marina; Tsao, Philip; Program, Million Veteran; Mercader, Josep; Hanis, Craig; Daly, Mark; Denny, Joshua; Gabriel, Stacey; Kathiresan, Sekar (2020)
    Author summary Cirrhosis is a leading cause of death worldwide. However, the genetic underpinnings of cirrhosis remain poorly understood. In this study, we analyze twelve thousand individuals with cirrhosis and identify a common missense variant in a gene called MARC1 that protects against cirrhosis. Carriers of this missense variant also have lower blood cholesterol levels, lower liver enzyme levels and reduced liver fat. We identify an additional two low-frequency coding variants in MARC1 that are also associated with lower cholesterol levels, lower liver enzyme levels and protection from cirrhosis. Finally, we identify an individual homozygous for a predicted loss-of-function variant in MARC1 who exhibits very low blood LDL cholesterol levels. These genetic findings suggest that MARC1 deficiency may lower blood cholesterol levels and protect against cirrhosis, pointing to MARC1 as a potential therapeutic target for liver disease. Analyzing 12,361 all-cause cirrhosis cases and 790,095 controls from eight cohorts, we identify a common missense variant in the Mitochondrial Amidoxime Reducing Component 1 gene (MARC1 p.A165T) that associates with protection from all-cause cirrhosis (OR 0.91, p = 2.3*10(-11)). This same variant also associates with lower levels of hepatic fat on computed tomographic imaging and lower odds of physician-diagnosed fatty liver as well as lower blood levels of alanine transaminase (-0.025 SD, 3.7*10(-43)), alkaline phosphatase (-0.025 SD, 1.2*10(-37)), total cholesterol (-0.030 SD, p = 1.9*10(-36)) and LDL cholesterol (-0.027 SD, p = 5.1*10(-30)) levels. We identified a series of additional MARC1 alleles (low-frequency missense p.M187K and rare protein-truncating p.R200Ter) that also associated with lower cholesterol levels, liver enzyme levels and reduced risk of cirrhosis (0 cirrhosis cases for 238 R200Ter carriers versus 17,046 cases of cirrhosis among 759,027 non-carriers, p = 0.04) suggesting that deficiency of the MARC1 enzyme may lower blood cholesterol levels and protect against cirrhosis.
  • Petäjä, Elina M.; Yki-Järvinen, Hannele (2016)
    Non-alcoholic fatty liver disease (NAFLD) covers a spectrum of disease ranging from simple steatosis (NAFL) to non-alcoholic steatohepatitis (NASH) and fibrosis. "Obese/Metabolic NAFLD" is closely associated with obesity and insulin resistance and therefore predisposes to type 2 diabetes and cardiovascular disease. NAFLD can also be caused by common genetic variants, the patatin-like phospholipase domain-containing 3 (PNPLA3) or the transmembrane 6 superfamily member 2 (TM6SF2). Since NAFL, irrespective of its cause, can progress to NASH and liver fibrosis, its definition is of interest. We reviewed the literature to identify data on definition of normal liver fat using liver histology and different imaging tools, and analyzed whether NAFLD caused by the gene variants is associated with insulin resistance. Histologically, normal liver fat content in liver biopsies is most commonly defined as macroscopic steatosis in less than 5% of hepatocytes. In the population-based Dallas Heart Study, the upper 95th percentile of liver fat measured by proton magnetic spectroscopy (1H-MRS) in healthy subjects was 5.6%, which corresponds to approximately 15% histological liver fat. When measured by magnetic resonance imaging (MRI)-based techniques such as the proton density fat fraction (PDFF), 5% macroscopic steatosis corresponds to a PDFF of 6% to 6.4%. In contrast to "Obese/metabolic NAFLD", NAFLD caused by genetic variants is not associated with insulin resistance. This implies that NAFLD is heterogeneous and that "Obese/Metabolic NAFLD" but not NAFLD due to the PNPLA3 or TM6SF2 genetic variants predisposes to type 2 diabetes and cardiovascular disease.
  • Anstee, Quentin M.; Darlay, Rebecca; Cockell, Simon; Meroni, Marica; Govaere, Olivier; Tiniakos, Dina; Burt, Alastair D.; Bedossa, Pierre; Palmer, Jeremy; Liu, Yang-Lin; Aithal, Guruprasad P.; Allison, Michael; Yki-Järvinen, Hannele; Vacca, Michele; Dufour, Jean-Francois; Invernizzi, Pietro; Prati, Daniele; Ekstedt, Mattias; Kechagias, Stergios; Francque, Sven; Petta, Salvatore; Bugianesi, Elisabetta; Clement, Karine; Ratziu, Vlad; Schattenberg, Jörn M.; Valenti, Luca; Day, Christopher P.; Cordell, Heather J.; Daly, Ann K. (2020)
    Background and Aims Genetic factors associated with non-alcoholic fatty liver disease (NAFLD) remain incompletely understood. To date, most GWAS studies have adopted radiologically assessed hepatic triglyceride content as reference phenotype and so cannot address steatohepatitis or fibrosis. We describe a genome-wide association study (GWAS) encompassing the full spectrum of histologically characterized NAFLD. Methods The GWAS involved 1483 European NAFLD cases and 17781 genetically-matched population controls. A replication cohort of 559 NAFLD cases and 945 controls was genotyped to confirm signals showing genome-wide or close to genome-wide significance. Results Case-control analysis identified signals showing p-values ≤ 5 x 10-8 at four locations (chromosome (chr) 2 GCKR/C2ORF16; chr4 HSD17B13; chr19 TM6SF2; chr22 PNPLA3) together with two other signals with p
  • Lallukka, S.; Yki-Jarvinen, H. (2016)
    Non-alcoholic fatty liver disease (NAFLD) covers a spectrum of liver disease from simple steatosis to non-alcoholic steatohepatitis (NASH) and cirrhosis. NAFLD is commonly associated with features of the metabolic/insulin resistance syndrome ('Metabolic/Obese NAFLD') and may therefore predict type 2 diabetes (T2DM). For this review, we searched for prospective studies examining whether NAFLD predicts T2DM, and if so, whether this occurs independently of factors such as age and obesity. These studies included NAFLD diagnosed by ultrasonography (n = 6) or liver enzymes (n = 14). All ultrasonography studies found NAFLD to predict the risk of T2DM independently of age, and in 4 out of 6 studies NAFLD was also a predictor independently of BMI. NAFLD was a predictor of T2DM in all 14 studies where NAFLD was diagnosed by liver enzymes. In 12 of these studies, ALT or AST or GGT were significant predictors of T2DM risk, independently of age and BMI. NAFLD, however, is heterogeneous and may also be caused by common genetic variants. The I148M variant in PNPLA3 and the E167K variant in TM6SF2 are both associated with increased liver fat content, but not features of the metabolic/insulin resistance syndrome. These genetic forms of NAFLD predict NASH and cirrhosis but not T2DM. Taken together these data imply that 'Metabolic/Obese NAFLD' predicts T2DM independently of age and obesity and support the role of hepatic insulin resistance in the pathogenesis of this disease. (C) 2016 Elsevier Ltd. All rights reserved.
  • EU-PNAFLD Investigators; GOLD Consortium; Teo, Kevin; Abeysekera, Kushala W. M.; Luukkonen, Panu K.; Yki-Järvinen, Hannele (2021)
    Background & Aims: A common genetic variant near MBOAT7 (rs641738C>T) has been previously associated with hepatic fat and advanced histology in NAFLD; however, these findings have not been consistently replicated in the literature. We aimed to establish whether rs641738C>T is a risk factor across the spectrum of NAFLD and to characterise its role in the regulation of related metabolic phenotypes through a meta-analysis. Methods: We performed a meta-analysis of studies with data on the association between rs641738C>T genotype and liver fat, NAFLD histology, and serum alanine aminotransferase (ALT), lipids or insulin. These included directly genotyped studies and population-level data from genome-wide association studies (GWAS). We performed a random effects meta-analysis using recessive, additive and dominant genetic models. Results: Data from 1,066,175 participants (9,688 with liver biopsies) across 42 studies were included in the meta-analysis. rs641738C>T was associated with higher liver fat on CT/MRI (+0.03 standard deviations [95% CI 0.02-0.05], p(z) = 4.8x10(-5)) and diagnosis of NAFLD (odds ratio [OR] 1.17 [95% CI 1.05-1.3], p(z) = 0.003) in Caucasian adults. The variant was also positively associated with presence of advanced fibrosis (OR 1.22 [95% CI 1.03-1.45], p(z) = 0.021) in Caucasian adults using a recessive model of inheritance (CC + CT vs. TT). Meta-analysis of data from previous GWAS found the variant to be associated with higher ALT (p(z) = 0.002) and lower serum triglycerides (p(z) = 1.5x10(-4)). rs641738C>T was not associated with fasting insulin and no effect was observed in children with NAFLD. Conclusions: Our study validates rs641738C>T near MBOAT7 as a risk factor for the presence and severity of NAFLD in individuals of European descent. Lay summary: Fatty liver disease is a common condition where fat builds up in the liver, which can cause liver inflammation and scarring (including 'cirrhosis'). It is closely linked to obesity and diabetes, but some genes are also thought to be important. We did this study to see whether one specific change ('variant') in one gene ('MBOAT7') was linked to fatty liver disease. We took data from over 40 published studies and found that this variant near MBOAT7 is linked to more severe fatty liver disease. This means that drugs designed to work on MBOAT7 could be useful for treating fatty liver disease. (C) 2020 European Association for the Study of the Liver. Published by Elsevier B.V.
  • Luukkonen, Panu K.; Qadri, Sami; Lehtimäki, Tiina E.; Juuti, Anne; Sammalkorpi, Henna; Penttilä, Anne K.; Hakkarainen, Antti; Orho-Melander, Marju; Arola, Johanna; Yki-Järvinen, Hannele (2021)
    Context: The I148M (rs738409-G) variant in PNPLA3 increases liver fat content but may be protective against cardiovascular disease. Insulin resistance (IR) amplifies the effect of PNPLA3-I148M on liver fat. Objective: To study whether PNPLA3-I148M confers an antihyperlipidemic effect in insulin-resistant patients. Design: Cross-sectional study comparing the impact of PNPLA3-I148M on plasma lipids and lipoproteins in 2 cohorts, both divided into groups based on rs738409-G allele carrier status and median HOMA-IR. Setting: Tertiary referral center. Patients: A total of 298 obese patients who underwent a liver biopsy during bariatric surgery (bariatric cohort: age 49 +/- 9 years, body mass index [BMI] 43.2 +/- 6.8 kg/m(2)), and 345 less obese volunteers in whom liver fat was measured by proton magnetic resonance spectroscopy (nonbariatric cohort: age 45 +/- 14 years, BMI 29.7 +/- 5.7 kg/m(2)). Main Outcome Measures: Nuclear magnetic resonance profiling of plasma lipids, lipoprotein particle subclasses and their composition. Results: In both cohorts, individuals carrying the PNPLA3-I148M variant had significantly higher liver fat content than noncarriers. In insulin-resistant and homozygous carriers, PNPLA3-I148M exerted a distinct antihyperlipidemic effect with decreased very-low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) particles and their constituents, and increased high-density lipoprotein particles and their constituents, compared with noncarriers. VLDL particles were smaller and LDL particles larger in PNPLA3-I148M carriers. These changes were geometrically opposite to those due to IR. PNPLA3-I148M did not have a measurable effect in patients with lower IR, and its effect was smaller albeit still significant in the less obese than in the obese cohort. Conclusions: PNPLA3-I148M confers an antiatherogenic plasma lipid profile particularly in insulin-resistant individuals.