Liver fatty acid binding protein (L-Fabp) modulates murine stellate cell activation and diet-induced nonalcoholic fatty liver disease

Abstract

Activation of hepatic stellate cells (HSCs) is crucial to the development of fibrosis in nonalcoholic fatty liver disease. Quiescent HSCs contain lipid droplets (LDs), whose depletion upon activation induces a fibrogenic gene program. Here we show that liver fatty acid-binding protein (L-Fabp), an abundant cytosolic protein that modulates fatty acid (FA) metabolism in enterocytes and hepatocytes also modulates HSC FA utilization and in turn regulates the fibrogenic program. L-Fabp expression decreased 10-fold following HSC activation, concomitant with depletion of LDs. Primary HSCs isolated from L-FABP−/− mice contain fewer LDs than wild type (WT) HSCs, and exhibit upregulated expression of genes involved in HSC activation. Adenoviral L-Fabp transduction inhibited activation of passaged WT HSCs and increased both the expression of prolipogenic genes and also augmented intracellular lipid accumulation, including triglyceride and FA, predominantly palmitate. Freshly isolated HSCs from L-FABP−/− mice correspondingly exhibited decreased palmitate in the free FA pool. To investigate whether L-FABP deletion promotes HSC activation in vivo, we fed L-FABP−/− and WT mice a high fat diet supplemented with trans-fatty acids and fructose (TFF). TFF-fed L-FABP−/− mice exhibited reduced hepatic steatosis along with decreased LD abundance and size compared to WT mice. In addition, TFF-fed L-FABP−/− mice exhibited decreased hepatic fibrosis, with reduced expression of fibrogenic genes, compared to WT mice. Conclusion L-FABP deletion attenuates both diet-induced hepatic steatosis and fibrogenesis, despite the observation that L-Fabp paradoxically promotes FA and LD accumulation and inhibits HSC activation in vitro. These findings highlight the importance of cell-specific modulation of hepatic lipid metabolism in promoting fibrogenesis in nonalcoholic fatty liver disease.

Perilipin 5 and liver fatty acid binding protein function to restore quiescence in mouse hepatic stellate cells

“…-/-) were generated and maintained as described previously (18). Wild-type male and female C57BL/6J mice were purchased from Jackson Laboratory, Bar Harbor, MA and were housed in a temperature-controlled animal facility (23°C) with a 12:12 h light-dark cycle and allowed free access to regular chow and water ad libitum.…”

“…Recombinant adenoviral Ad-L-Fabp with expression of FLAG epitope-tagged L-Fabp, or recombinant adenoviral Ad-LacZ with expression of LacZ were previously described and used (18). Ad-I-Fabp was constructed using a mouse I-Fabp cDNA containing 3 copies of the FLAG epitope tag at the amino terminus and cloned into the pVQ AdCMV shuttle plasmid for recombination, amplification and purification (ViraQuest Labs).…”

Perilipin 5 restores the formation of lipid droplets in activated hepatic stellate cells and inhibits their activation

“…Hepatic steatosis with fibrosis in one group of mice (n = 10) was induced by feeding a high trans-fat diet supplemented with high fructose corn syrup for 16 weeks as described, 24 with minor modifications, including drinking water in bottles and without removal of cage racks. 25 The control group (n = 10) were fed a chow diet. After sacrifice, small pieces of different lobes from each mouse of the obese mouse model were collected for immuno-histochemical studies by fixation with formalin (10%) and subsequent embedment with paraffin.…”

“…25 Mice fed a HFD were previously characterized and hepatic fibrosis in the mice was evaluated by real-time PCR analyses of pro-fibrogenic genes and quantitation of picro-Sirius Red and trichrome staining of collagens in liver tissue. 25 As shown in Figure 1a, compared to mice in the chow group, mice fed HFD showed apparent deposition of extracellular matrix in the liver demonstrated by Sirius Red stain, indicating hepatic fibrosis in the group of HFD mice. Immuno-histochemical studies showed positive stain of α-SMA, a unique marker for activated HSC, in the liver in the group of HFD mice.…”

Molecular characterization, tissue expression, and polymorphism analysis of liver-type fatty acid binding protein in Landes geese

“…The lack of L-FABP not only modified intestinal fatty acid composition, but also affected adenoma formation in ApcMin/+ mice (Newberry et al, 2003;Seneshaw et al, 2005;Dharmarajan et al, 2013). Recent studies indicated that L-FABP can be used as a novel marker for diet-induced nonalcoholic fatty liver disease and organ damage caused by specific types of cancer (Relija et al, 2010;Chen et al, 2013).…”