TY - JOUR
T1 - Distinct contributions of metabolic dysfunction and genetic risk factors in the pathogenesis of non-alcoholic fatty liver disease
AU - Luukkonen, Panu K.
AU - Qadri, Sami
AU - Ahlholm, Noora
AU - Porthan, Kimmo
AU - Männistö, Ville
AU - Sammalkorpi, Henna
AU - Penttilä, Anne K.
AU - Hakkarainen, Antti
AU - Lehtimäki, Tiina E.
AU - Gaggini, Melania
AU - Gastaldelli, Amalia
AU - Ala-Korpela, Mika
AU - Orho-Melander, Marju
AU - Arola, Johanna
AU - Juuti, Anne
AU - Pihlajamäki, Jussi
AU - Hodson, Leanne
AU - Yki-Järvinen, Hannele
N1 - Funding Information:
This study was supported by Academy of Finland Grant 309263 (H.Y.-J.) and Grant 138006 (J.P.), EU H2020 project ?Elucidating Pathways of Steatohepatitis? EPoS Grant 634413 (H.Y.-J.), H2020-JTI-IMI2 EU project 777377-2 Liver Investigation: Testing Marker Utility in Steatohepatitis (LITMUS) (H.Y.-J.), Government Funding (H.Y.-J.), Novo Nordisk Foundation (H.Y.-J., P.K.L., M.A.-K.), Ralph Gr?sbeck Scholarship of the Minerva Foundation (P.K.L.), Novo Nordisk Foundation (P.K.L.), Juho Vainio Foundation (J.P.), Finnish Medical Foundation (V.M.), British Heart Foundation Senior Research Fellowship in Basic Science (FS/15/56/31645) (L.H.) and Kuopio University Hospital Project grant (J.P., EVO/VTR grants 2005-2019).
Funding Information:
This study was supported by Academy of Finland Grant 309263 (H.Y.-J.) and Grant 138006 (J.P.), EU H2020 project ‘Elucidating Pathways of Steatohepatitis’ EPoS Grant 634413 (H.Y.-J.), H2020-JTI-IMI2 EU project 777377-2 Liver Investigation: Testing Marker Utility in Steatohepatitis (LITMUS) (H.Y.-J.), Government Funding (H.Y.-J.), Novo Nordisk Foundation (H.Y.-J., P.K.L., M.A.-K.), Ralph Gräsbeck Scholarship of the Minerva Foundation (P.K.L.), Novo Nordisk Foundation (P.K.L.), Juho Vainio Foundation (J.P.), Finnish Medical Foundation (V.M.), British Heart Foundation Senior Research Fellowship in Basic Science (FS/15/56/31645) (L.H.) and Kuopio University Hospital Project grant (J.P., EVO/VTR grants 2005-2019).
Publisher Copyright:
© 2021 The Author(s)
PY - 2022/3
Y1 - 2022/3
N2 - Background & Aims: There is substantial inter-individual variability in the risk of non-alcoholic fatty liver disease (NAFLD). Part of which is explained by insulin resistance (IR) (‘MetComp’) and part by common modifiers of genetic risk (‘GenComp’). We examined how IR on the one hand and genetic risk on the other contribute to the pathogenesis of NAFLD. Methods: We studied 846 individuals: 492 were obese patients with liver histology and 354 were individuals who underwent intrahepatic triglyceride measurement by proton magnetic resonance spectroscopy. A genetic risk score was calculated using the number of risk alleles in PNPLA3, TM6SF2, MBOAT7, HSD17B13 and MARC1. Substrate concentrations were assessed by serum NMR metabolomics. In subsets of participants, non-esterified fatty acids (NEFAs) and their flux were assessed by D5-glycerol and hyperinsulinemic-euglycemic clamp (n = 41), and hepatic de novo lipogenesis (DNL) was measured by D2O (n = 61). Results: We found that substrate surplus (increased concentrations of 28 serum metabolites including glucose, glycolytic intermediates, and amino acids; increased NEFAs and their flux; increased DNL) characterized the ‘MetComp’. In contrast, the ‘GenComp’ was not accompanied by any substrate excess but was characterized by an increased hepatic mitochondrial redox state, as determined by serum β-hydroxybutyrate/acetoacetate ratio, and inhibition of hepatic pathways dependent on tricarboxylic acid cycle activity, such as DNL. Serum β-hydroxybutyrate/acetoacetate ratio correlated strongly with all histological features of NAFLD. IR and hepatic mitochondrial redox state conferred additive increases in histological features of NAFLD. Conclusions: These data show that the mechanisms underlying ‘Metabolic’ and ‘Genetic’ components of NAFLD are fundamentally different. These findings may have implications with respect to the diagnosis and treatment of NAFLD. Lay summary: The pathogenesis of non-alcoholic fatty liver disease can be explained in part by a metabolic component, including obesity, and in part by a genetic component. Herein, we demonstrate that the mechanisms underlying these components are fundamentally different: the metabolic component is characterized by hepatic oversupply of substrates, such as sugars, lipids and amino acids. In contrast, the genetic component is characterized by impaired hepatic mitochondrial function, making the liver less able to metabolize these substrates.
AB - Background & Aims: There is substantial inter-individual variability in the risk of non-alcoholic fatty liver disease (NAFLD). Part of which is explained by insulin resistance (IR) (‘MetComp’) and part by common modifiers of genetic risk (‘GenComp’). We examined how IR on the one hand and genetic risk on the other contribute to the pathogenesis of NAFLD. Methods: We studied 846 individuals: 492 were obese patients with liver histology and 354 were individuals who underwent intrahepatic triglyceride measurement by proton magnetic resonance spectroscopy. A genetic risk score was calculated using the number of risk alleles in PNPLA3, TM6SF2, MBOAT7, HSD17B13 and MARC1. Substrate concentrations were assessed by serum NMR metabolomics. In subsets of participants, non-esterified fatty acids (NEFAs) and their flux were assessed by D5-glycerol and hyperinsulinemic-euglycemic clamp (n = 41), and hepatic de novo lipogenesis (DNL) was measured by D2O (n = 61). Results: We found that substrate surplus (increased concentrations of 28 serum metabolites including glucose, glycolytic intermediates, and amino acids; increased NEFAs and their flux; increased DNL) characterized the ‘MetComp’. In contrast, the ‘GenComp’ was not accompanied by any substrate excess but was characterized by an increased hepatic mitochondrial redox state, as determined by serum β-hydroxybutyrate/acetoacetate ratio, and inhibition of hepatic pathways dependent on tricarboxylic acid cycle activity, such as DNL. Serum β-hydroxybutyrate/acetoacetate ratio correlated strongly with all histological features of NAFLD. IR and hepatic mitochondrial redox state conferred additive increases in histological features of NAFLD. Conclusions: These data show that the mechanisms underlying ‘Metabolic’ and ‘Genetic’ components of NAFLD are fundamentally different. These findings may have implications with respect to the diagnosis and treatment of NAFLD. Lay summary: The pathogenesis of non-alcoholic fatty liver disease can be explained in part by a metabolic component, including obesity, and in part by a genetic component. Herein, we demonstrate that the mechanisms underlying these components are fundamentally different: the metabolic component is characterized by hepatic oversupply of substrates, such as sugars, lipids and amino acids. In contrast, the genetic component is characterized by impaired hepatic mitochondrial function, making the liver less able to metabolize these substrates.
KW - adipose tissue lipolysis
KW - de novo lipogenesis
KW - hepatic mitochondrial redox state
KW - HSD17B13
KW - insulin resistance
KW - MARC1
KW - MBOAT7
KW - metabolomics
KW - PNPLA3
KW - TM6SF2
UR - http://www.scopus.com/inward/record.url?scp=85120755150&partnerID=8YFLogxK
U2 - 10.1016/j.jhep.2021.10.013
DO - 10.1016/j.jhep.2021.10.013
M3 - Article
AN - SCOPUS:85120755150
SN - 0168-8278
VL - 76
SP - 526
EP - 535
JO - Journal of Hepatology
JF - Journal of Hepatology
IS - 3
ER -