Susceptibility of L-FABP−/− mice to oxidative stress in early-stage alcoholic liver

James J. Galligan,Martin Ronis,Kelly Mercer,Nicholas O. Davidson,Colin T. Shearn,Dennis R. Petersen,Rebecca L. Smathers,David J. Orlicky,Kristofer S. Fritz

doi:10.1194/jlr.m034892

Abstract

Chronic ethanol consumption is a prominent cause of liver disease worldwide. Dysregulation of an important lipid uptake and trafficking gene, liver-fatty acid binding protein (L-FABP), may contribute to alterations in lipid homeostasis during early-stage alcoholic liver. We have reported the detrimental effects of ethanol on the expression of L-FABP and hypothesize this may deleteriously impact metabolic networks regulating fatty acids. Male wild-type (WT) and L-FABP(-/-) mice were fed a modified Lieber-DeCarli liquid diet for six weeks. To assess the response to chronic ethanol ingestion, standard biochemical indicators for alcoholic liver disease (ALD) and oxidative stress were measured. Ethanol ingestion resulted in attenuation of hepatic triglyceride accumulation and elevation of cholesterol in L-FABP(-/-) mice. Lipidomics analysis validated multiple alterations in hepatic lipids resulting from ethanol treatment. Increased immunohistochemical staining for the reactive aldehydes 4-hydroxynonenal and malondialdehyde were observed in WT mice ingesting ethanol; however, L-FABP(-/-) mice displayed prominent protein adducts in liver sections evaluated from pair-fed and ethanol-fed mice. Likewise, alterations in glutathione, thiobarbituric acid reactive substances (TBARS), 8-isoprostanes, and protein carbonyl content all indicated L-FABP(-/-) mice exhibit high sustained oxidative stress in the liver. These data establish that L-FABP is an indirect antioxidant protein essential for sequestering FFA and that its impairment could contribute to in the pathogenesis of ALD.

Highlights

Chronic ethanol consumption is a prominent cause of liver disease worldwide
Given the proposed role of liver-fatty acid binding protein (L-FABP) in hepatic lipid trafficking, it was anticipated that significant alterations in lipid homeostasis would occur in mice chronically consuming ethanol
L-FABPϪ/Ϫ mice were moderately protected from ethanol-induced steatosis, similar to those subjected to high-fat diets [10, 23, 43]

Summary

Introduction

Chronic ethanol consumption is a prominent cause of liver disease worldwide. Dysregulation of an important lipid uptake and trafficking gene, liver-fatty acid binding protein (L-FABP), may contribute to alterations in lipid homeostasis during early-stage alcoholic liver. To assess the response to chronic ethanol ingestion, standard biochemical indicators for alcoholic liver disease (ALD) and oxidative stress were measured. Alterations in glutathione, thiobarbituric acid reactive substances (TBARS), 8-isoprostanes, and protein carbonyl content all indicated L-FABP؊/؊ mice exhibit high sustained oxidative stress in the liver. These data establish that L-FABP is an indirect antioxidant protein essential for sequestering FFA and that its impairment could contribute to in the pathogenesis of ALD.—Smathers, R. Susceptibility of L-FABP؊/؊ mice to oxidative stress in early-stage alcoholic liver. It has been hypothesized that early-stage ALD, namely steatosis or fatty liver, occurs as a result of the dysregulation of fatty acids (FA) through synthesis and oxidation, storage, and/ or import/export mechanisms [3].

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Results

Conclusion