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Alcohol-associated liver disease (ALD) is a global burden of healthcare and remains a major cause of morbidity and mortality worldwide. ALD includes a spectrum of injuries that progresses from hepatic steatosis, alcoholic hepatitis to alcohol-associated cirrhosis and even hepatocellular carcinoma with continued alcohol misuse. The development of ALD depends on several factors, including genetics. The liver enzyme phosphatidylethanolamine methyltransferase (PEMT) catalyzes three sequential methyl transfers to phosphatidylethanolamine, generating phosphatidylcholine (PC). The PC generated with PEMT-mediated catalysis is preferentially used in very-low-density-lipoprotein (VLDL) assembly and is required for its normal biogenesis and secretion (1-3). Alcohol affects the methylation potential and impairs PEMT activity, which by inhibiting VLDL synthesis contributes to the development of hepatic steatosis. Polymorphisms in the human PEMT gene causing loss of function confer susceptibility to metabolic-associated steatohepatitis.
Based on these considerations, we hypothesized that PEMT deletion would exacerbate alcohol-induced liver injury.
Animal Handling and Diet:
Male and female wildtype (WT) and PEMT knock out (KO) mice (12 weeks of age) were subjected to ethanol binge feeding model. The animals were gavaged with maltose dextrin or ethanol (5g/Kg BW) twice, 12 hours apart. The mice were euthanized eight hours after the second dose, where the blood and liver were collected for the following analyses:
AST and ALT levels: Serum AST and ALT were analyzed using a VITROS 5.1 FS Chemistry System.
Hepatic histopathology: Neutral-buffered formalin fixed liver sections stained with hematoxylin & eosin (H & E) and picrosirius red were imaged using a Keyence BZ-810 microscope.
HPLC Analysis: Liver tissues were homogenized in 0.5N perchloric acid and subjected to HPLC analysis to determine S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) levels (3,4) The SAM:SAH ratio, or methylation index, was calculated, as detailed (3,4).
Triglyceride Quantification: Lipids were extracted by Folch method (6) and triglyceride levels were quantified using the Thermo DNA Kit (3,4).
Enzymatic Activity: Lysosomal acid lipase and proteasome activities were determined in liver homogenates, as detailed (7)
Statistical Analyses: Data are expressed as mean values ± standard error (SE). Values not sharing a common subscript letter are statistically different, p < 0.05.
We found deletion of PEMT exacerbates acute alcohol-induced liver injury in both males and females as evidenced by:
•Increased AST and ALT levels
•Increased fat accumulation by histopathological assessment
•Decreased SAM levels causing a reduction in the methylation potential •Increased hepatic triglycerides •Decreased lysosomal acid lipase activity •Decreased proteasome activity
Hepatic steatosis, alcoholic hepatitis, phosphatidylethanolamine methyltransferase, Alcohol-associated cirrhosis, hepatocellular carcinoma, alcohol misuse, Alcohol-associated liver disease, ALD, PEMT, SAM:SAH, fatty liver, hepatic triglycerides, steatosis, acute alcohol-induced liver injury
Gardner, Jessica A.; Arumugam, Madan Kumar; Chava, Srinivas; Perumal, Sathish Kumar; and Kharbanda, Kusum K., "Phosphatidylethanolamine Methyltransferase Deficiency Exacerbates Acute Alcohol-Induced Liver Injury" (2022). Posters: 2022 Summer Undergraduate Research Program. 35.