Soybean polyenylphosphatidylcholine (PPC) is beneficial in liver and extrahepatic tissue injury: An update in experimental research.

Polyenylphosphatidylcholine (PPC) is a purified polyunsaturated phosphatidylcholine extract of soybeans. This article updates PPC's beneficial effects on various forms of liver cell injury and other tissues in experimental research. PPC downregulates hepatocyte CYP2E1 expression and associated hepatotoxicity, as well as attenuates oxidative stress, apoptosis, lipoprotein oxidation and steatosis in alcoholic and nonalcoholic liver injury. PPC inhibits pro-inflammatory cytokine production, while stimulating anti-inflammatory cytokine secretion in ethanol or lipopolysaccharide-stimulated Kupffer cells/macrophages. It promotes M2-type macrophage polarization and metabolic reprogramming of glucose and lipid metabolism. PPC mitigates steatosis in NAFLD through inhibiting polarization of pro-inflammatory M1-type Kupffer cells, alleviating metabolic inflammation, remodeling hepatic lipid metabolism, correcting imbalances between lipogenesis and lipolysis and enhancing lipoprotein secretion from hepatocytes. PPC is antifibrotic by preventing progression of alcoholic hepatic fibrosis in baboons and also prevents CCl4-induced fibrosis in rats. PPC supplementation replenishes the phosphatidylcholine content of damaged cell membranes, resulting in increased membrane fluidity and functioning. Phosphatidylcholine repletion prevents increased membrane curvature of the endoplasmic reticulum and Golgi and decreases sterol regulatory element binding protein-1-mediated lipogenesis, reducing steatosis. PPC remodels gut microbiota and affects hepatic lipid metabolism via the gut-hepatic-axis and also alleviates brain inflammatory responses and cognitive impairment via the gut-brain-axis. Additionally, PPC protects extrahepatic tissues from injury caused by various toxic compounds by reducing oxidative stress, inflammation, and membrane damage. It also stimulates liver regeneration, enhances sensitivity of cancer cells to radiotherapy/chemotherapy, and inhibits experimental hepatocarcinogenesis. PPC's beneficial effects justify it as a supportive treatment of liver disease.

A review of hepatic fibrosis-associated histopathology in aged cadavers.

This article reviews hepatic fibrosis-associated histopathology of aged cadavers (mean age 82 years). A study of 68 livers identified steatosis in 35.5%, central vein fibrosis in 49.2%, perisinusoidal fibrosis in 63.2%, portal tract fibrosis in 47.7%, septa formation in 44.1%, bridging fibrosis in 30.8%, and cirrhosis in 4.4% of the samples as well as one hepatocellular carcinoma and six metastatic tumors. Other studies have revealed that collagens I, III, IV, V, and VI and fibronectin constitute the matrices of fibrous central veins, perisinusoidal space, portal tracts, and septa. Elastin is rich in portal tracts and fibrous septa but absent from the perisinusoidal space. Hepatic stellate cells are ubiquitous in the liver parenchyma while myofibroblasts localize in fibrotic foci. Factor VIII-related antigen expression signals sinusoidal to systemic vascular endothelium transformation while collagen IV and laminin codistribution indicates formation of perisinusoidal membranes. Their coincidence reflects focalized capillarization of sinusoids in the aged liver. In response to fibrogenesis, hepatic progenitor cells residing in the canal of Hering in the periportal parenchyma undergo expansion and migration deep into the lobule. Concomitantly, intermediate hepatocyte-like cells increase in advanced fibrosis stages, which is possibly related to hepatic regeneration. Metabolic zonation of glutamine synthetase expands from the perivenous to non-perivenous parenchyma in fibrosis progression but its expression is lost in cirrhosis, while cytochrome P-4502E1 expression is maintained in centrilobular and midlobular zones in fibrosis progression and expressed in cirrhosis. Hence, cadaveric livers provide a platform for further investigation of hepatic histopathologies associated with the aging liver.

Lipid droplets, the Holy Grail of hepatic stellate cells: In health and hepatic fibrosis.

Lipid droplets (LDs) are distinct morphological markers of hepatic stellate cells (HSCs). They are composed of a core of predominantly retinyl esters and triacylglycerols surrounded by a phospholipid layer; the latter harbors perilipins 2, 3, and 5, which help control LD lipolysis. Electron microscopy distinguishes between Types I and II LDs. Type I LDs are surrounded by acid phosphatase-positive lysosomes, which likely digest LDs. LD count and retinoid concentration are modulated by vitamin A intake. Alcohol consumption depletes hepatic retinoids and HSC LDs, with concomitant transformation of HSCs to fibrogenic myofibroblast-like cells. LD loss and accompanying HSC activation occur in HSC cell culture models. Loss of LDs is a consequence of and not a prerequisite for HSC activation. LDs are endowed with enzymes for synthesizing retinyl esters and triacylglycerols as well as neutral lipases and lysosomal acid lipase for breaking down LDs. HSCs have two distinct metabolic LD pools: an "original" pool in quiescent HSCs and a "new" pool emerging in HSC activation; this two-pool model provides a platform for analyzing LD dynamics in HSC activation. Besides lipolysis, LDs are degraded by lipophagy; however, the coordination between and relative contributions of these two pathways to LD removal are unclear. While induction of autophagy accelerates LD loss in quiescent HSCs and promotes HSC activation, blocking autophagy impairs LD degradation and inhibits HSC activation and fibrosis. This article is a critique of five decades of investigations into the morphology, molecular structure, synthesis, and degradation of LDs associated with HSC activation and fibrosis.

Alcohol-associated capillarization of sinusoids: A critique since the discovery by Schaffner and Popper in 1963.

This article reviews the literature on capillarization of hepatic sinusoids since its discovery in 1963. Liver sinusoidal endothelial cells are uniquely fenestrated and lack an underlying basement membrane. In chronic liver disease, the sinusoids capillarize and transform into systemic capillaries, a process termed capillarization of sinusoids. The histopathology is marked by defenestration, basement membrane formation, and space of Disse fibrogenesis. Capillarized sinusoids compromise the bidirectional exchange of materials between sinusoids and hepatocytes, leading to hepatocellular dysfunction. Sinusoidal capillarization was first described in active cirrhosis of alcoholics in 1963. Since then, it has been found in early and progressive stages of alcoholic hepatic fibrosis before the onset of cirrhosis. The sinusoidal structure is not altered in alcoholic steatosis without fibrosis. Defenestration impairs the ability of the endothelium to filter chylomicron remnants from sinusoids into the Disse's space, contributing to alcohol-induced postprandial hyperlipidemia and possibly atherosclerosis. Ethanol also modulates the fenestration dynamics in animals. In baboons, chronic alcohol consumption diminishes endothelial porosity in concomitance with hepatic fibrogenesis and in rats defenestrates the endothelium in the absence of fibrosis, and sometimes capillarizes the sinusoids. Acute ethanol ingestion enlarges fenestrations in rats and contracts fenestrations in rabbits. In sinusoidal endothelial cell culture, ethanol elicits fenestration dilation, which is likely related to its interaction with fenestration-associated cytoskeleton. Ethanol potentiates sinusoidal injury caused by cocaine, acetaminophen or lipopolysaccharide in mice and rats. Understanding ethanol's mechanisms on pathogenesis of sinusoidal capillarization and fenestration dynamics will lead to development of methods to prevent risks for atherosclerosis in alcoholism.

Hepatic sinusoids versus central veins: Structures, markers, angiocrines, and roles in liver regeneration and homeostasis.

The blood circulates through the hepatic sinusoids delivering nutrients and oxygen to the liver parenchyma and drains into the hepatic central vein, yet the structures and phenotypes of these vessels are distinctively different. Sinusoidal endothelial cells are uniquely fenestrated, lack basal lamina and possess organelles involved in endocytosis, pinocytosis, degradation, synthesis and secretion. Hepatic central veins are nonfenestrated but are also active in synthesis and secretion. Endothelial cells of sinusoids and central veins secrete angiocrines that play respective roles in hepatic regeneration and metabolic homeostasis. The list of markers for identifying sinusoidal endothelial cells is long and their terminologies are complex. Further, their uses vary in different investigations and, in some instances, could be confusing. Central vein markers are fewer but more distinctive. Here we analyze and categorize the molecular pathways/modules associated with the sinusoid-mediated liver regeneration in response to partial hepatectomy and chemical-induced acute or chronic injury. Similarly, we highlight the findings that central vein-derived angiocrines interact with Wnt/ß-catenin in perivenous hepatocytes to direct gene expression and maintain pericentral metabolic zonation. The proposal that perivenous hepatocytes behave as stem/progenitor cells to provoke hepatic homeostatic cell renewal is reevaluated and newer concepts of broad zonal distribution of hepatocyte proliferation in liver homeostasis and regeneration are updated. Thus, this review integrates the structures, biology and physiology of liver sinusoids and central veins in mediating hepatic regeneration and metabolic homeostasis.

The Hepatic Central Vein: Structure, Fibrosis, and Role in Liver Biology.

The hepatic central vein is a primary source of Wnt2, Wnt9b, and R-spondin3. These angiocrines activate ß-catenin signaling to regulate hepatic metabolic zonation and perivenous gene expression in mice. Little is known about the central vein ultrastructure. Here, we describe the morphological-functional correlates of the central vein and its draining and branching patterns. Central vein fibrosis occurs in liver disease and is often accompanied by perivenous perisinusoidal fibrosis, which may affect perivenous gene expression. We review the biological properties of perivenous hepatocytes and glutamine synthetase that serve as a biomarker of perivenous hepatocytes. Glutamine synthetase and P4502E1 are indicators of ß-catenin activity in centrilobular liver injury and regeneration. The Wnt/ß-catenin pathway is the master regulator of hepatic metabolic zonation and perivenous gene expression and is modulated by the R-spondin-LGR4/5-ZNRF3/RNF43 module. We examined the structures of the molecules of these pathways and their involvements in liver biology. Central vein-derived Wnts and R-spondin3 participate in the cellular-molecular circuitry of the Wnt/ß-catenin and R-spondin-LGR4/5-ZNRF3/RNF43 module. The transport and secretion of lipidated Wnts in Wnt-producing cells require Wntless protein. Secreted Wnts are carried on exosomes in the extracellular matrix to responder cells. The modes of release of Wnts and R-spondin3 from central veins and their transit in the venular wall toward perivenous hepatocytes are unknown. We hypothesize that central vein fibrosis may impact perivenous gene expression. The proposal that the central vein constitutes an anatomical niche of perivenous stem cells that subserve homeostatic hepatic renewal still needs studies using additional mouse models for validation. Anat Rec, 2019. © 2019 American Association for Anatomy Anat Rec, 303:1747-1767, 2020. © 2019 American Association for Anatomy.

Basement Membrane Type IV Collagen and Laminin: An Overview of Their Biology and Value as Fibrosis Biomarkers of Liver Disease.

Basement membranes provide structural support to epithelium, endothelium, muscles, fat cells, Schwann cells, and axons. Basement membranes are multifunctional: they modulate cellular behavior, regulate organogenesis, promote tissue repair, form a barrier to filtration and tumor metastasis, bind growth factors, and mediate angiogenesis. All basement membranes contain type IV collagen (Col IV), laminin, nidogen, and perlecan. Col IV and laminin self-assemble into two independent supramolecular networks that are linked to nidogen and perlecan to form a morphological discernable basement membrane/basal lamina. The triple helical region, 7S domain and NCI domain of Col IV, laminin and laminin fragment P1 have been evaluated as noninvasive fibrosis biomarkers of alcoholic liver disease, viral hepatitis, and nonalcoholic fatty liver disease. Elevated serum Col IV and laminin are related to degrees of fibrosis and severity of hepatitis, and may reflect hepatic basement membrane metabolism. But the serum assays have not been linked to disclosing the anatomical sites and lobular distribution of perisinusoidal basement membrane formation in the liver. Hepatic sinusoids normally lack a basement membrane, although Col IV is a normal matrix component of the space of Disse. In liver disease, laminin deposits in the space of Disse and codistributes with Col IV, forming a perisinusoidal basement membrane. Concomitantly, the sinusoidal endothelium loses its fenestrae and is transformed into vascular type endothelium. These changes lead to capillarization of hepatic sinusoids, a significant pathology that impairs hepatic function. Accordingly, codistribution of Col IV and laminin serves as histochemical marker of perisinusoidal basement membrane formation in liver disease. Anat Rec, 300:1371-1390, 2017. © 2017 Wiley Periodicals, Inc.

Type V Collagen in Health, Disease, and Fibrosis.

Type V collagen (COLV) is a regulatory fibril-forming collagen. It has at least three different molecular isoforms-α1(V)2 α2(V), α1(V)3, and α1(V)α2(V)α3(V)-formed by combinations of three different polypeptide α chains-α1(V), α2(V), and α3(V). COL V is a relatively minor collagen of the extracellular matrix (ECM). Morphologically, COLV occurs as heterotypic fibrils with type I collagen (COLI), microfilaments, or 12-nm-thick fibrils. COLV is synthesized in various mesenchymal cells and its gene expression is modulated by TGF-ß and growth factors. While resistant to digestion by interstitial collagenases, native and denatured COLV are degraded by metalloproteinases and gelatinases, thereby promoting ECM remodeling. COLV interacts with matrix collagens and structural proteins, conferring structural integrity to tissue scaffolds. It binds matrix macromolecules, modulating cellular behavior, and functions. COLV co-assembles with COLI into heterotypic fibrils in the cornea and skin dermis, acting as a dominant regulator of collagen fibrillogenesis. COLV deficiency is associated with loss of corneal transparency and classic Ehlers-Danlos syndrome, while COLV overexpression is found in cancer, granulation tissue, inflammation, atherosclerosis, and fibrosis of lungs, skin, kidneys, adipose tissue, and liver. COLV isoform containing the α3(V) chain is involved in mediating pancreatic islet cell functions. In the liver, COLV is a minor but regular component of the ECM. Increases in COLV are associated with both early and advanced hepatic fibrosis. The neoepitopes of COLV have been shown to be a useful noninvasive serum biomarker for assessing fibrotic progression and resolution in experimental hepatic fibrosis. COLV is multifunctional in health, disease, and fibrosis.

Factor VIII-Related Antigen Detects Phenotypic Change of Sinusoidal to Vascular Endothelium in Hepatic Fibrosis of Elderly Cadavers.

In advanced stages of hepatic fibrosis, the liver sinusoidal endothelium transforms to vascular endothelium with accompanying expression of factor VIII-related antigen (FVIIIRAg), a phenotypic marker of vascular endothelial cells. Liver fibrosis has been shown to be associated with aging and was found to be prevalent in elderly cadavers. Using immunohistochemistry, we studied FVIIIRAg expression in the livers of elderly cadavers with progressive stages of fibrosis. The vascular endothelium of portal tracts and central veins was stained for FVIIIRAg, providing an internal positive control. The incidence of FVIIIRAg expression was low in the sinusoids of livers that showed minimal fibrosis or perisinusoidal fibrosis but was increased in livers with advanced fibrosis (i.e., septa formation, bridging fibrosis, and cirrhosis). FVIIIRAg positive sinusoidal endothelial cells were distributed in loose aggregates in the periportal, periseptal, and midlobular parenchyma and were found less frequently in the centrilobular area. FVIIIRAg immune deposits appeared patchy and discontinuous along the sinusoidal lining, likely representing focalized transformation of sinusoidal to vascular endothelium. There was a discrete localization of FVIIIRAg immunoreactivity in the foci of severe parenchymal fibrosis. Conclusion. FVIIIRAg is a reliable marker for detecting the transformation of sinusoidal to vascular endothelium in advanced liver fibrosis in elderly cadavers.

Codistribution of collagen type IV and laminin in liver fibrosis of elderly cadavers: immunohistochemical marker of perisinusoidal basement membrane formation.

Liver sinusoids are lined by a fenestrated endothelium that lacks a basement membrane. Formation of perisinusoidal basement membranes beneath the endothelium is an integral feature of capillarization of sinusoids that is a significant pathology found in advanced fibrosis. Liver fibrosis is prevalent in elderly cadavers; however, basement membrane formation in these liver samples has yet to be studied. Collagen type IV and laminin are major basement membrane proteins and their codistribution around sinusoids provides an immunohistochemical marker of basement membrane formation. Here, we examined the intralobular sites of perisinusoidal basement membrane formation in elderly cadaveric livers having various stages of fibrosis. Collagen IV and laminin codistributed in basement membranes of portal and septal ductular and vascular structures, providing a positive control. In the parenchyma, collagen IV immunostaining of sinusoids was panlobular in all stages of fibrosis, and the stain was continuous along the sinusoids. In contrast, laminin was not detected in livers, showing minimal fibrotic change. It was rarely seen in perisinusoidal/pericellular fibrosis, but frequently in septa formation, bridging fibrosis, and cirrhosis. The laminin stain was patchy, occurring principally in sinusoids of periportal and periseptal areas, less commonly in mid-lobular and rarely in centrilobular areas. Consecutive sections revealed that laminin codistributed with collagen IV in these sinusoidal locations, thus marking the sites of perisinusoidal basement membrane formation in aged fibrotic livers. This development is presumably related to aging of the liver and exacerbated by liver injury caused by advanced liver fibrosis, possibly resulting in sinusoidal capillarization.

Liver fibrosis in elderly cadavers: localization of collagen types I, III, and IV, α-smooth muscle actin, and elastic fibers.

We have shown a high prevalence of liver fibrosis in elderly cadavers with diverse causes of death by Sirius red stain; however, the various collagen types in these samples have yet to be evaluated. To further characterize the histopathology of the fibrotic lesions in the livers of these elderly cadavers, this study used immunohistochemistry and histochemistry to identify the principal collagens produced in liver fibrosis, fibrogenic cells and elastic fibers. Collagen I and III immunoreactions were found to colocalize in collagen fibers of fibrotic central veins, perisinusoidal fibrotic foci, portal tract stroma, and fibrous septa. α-Smooth muscle actin-expressing perisinusoidal hepatic stellate cells (HSCs), as well as perivenular, portal, and septal myofibroblasts, were closely associated with collagen fibers, reflecting their fibrogenic functions. HSCs and myofibroblasts were also noted to express collagen IV, which may contribute to production of basal lamina-like structures. In fibrotic livers, the sinusoidal lining showed variable immunostaining for collagen IV. Collagen IV immunostaining revealed vascular proliferation and atypical ductular reaction at the portal-septal parenchymal borders, as well as capillary-like vessels in the lobular parenchyma. While elastic fibers were absent in the space of Disse, they were found to codistribute with collagens in portal tracts, fibrous septa and central veins. Our combined assessment of collagen types, HSCs, myofibroblasts, and elastic fibers is significant in understanding the histopathology of fibrosis in the aging liver.

Hepatic steatosis, fibrosis, and cancer in elderly cadavers.

The incidence of hepatic steatosis, fibrosis, and cancer in the elderly population remains unknown. Human cadavers used in anatomy teaching, which come largely from older adults, may provide liver tissue for examining their pathologies. Livers were obtained from 68 cadavers (mean age 82.1 ± 10.4 years) with diverse causes of death in the Anatomy course at Mount Sinai School of Medicine. Paraffin sections were stained with hematoxylin and eosin and Sirius red and evaluated for steatosis, fibrosis, cancer, and lipofuscin. Tissue preservation was graded as good in 38.2% of the embalmed livers, fair in 36.7%, and poor in 25.0%. Steatosis was observed in 35.3% of the livers, central vein fibrosis in 49.2%, perisinusoidal fibrosis in 63.2%, portal tract (PT) fibrosis in 47.0%, septa formation in 44.1%, bridging fibrosis in 30.8%, and cirrhosis in 4.4%. One hepatocellular carcinoma (HCC) and six metastatic tumors were detected. Lobular inflammation occurred in 20.8% of the livers and PT inflammation in 38.8%. Nine livers showed minimal change. Lipofuscin was detected in 60.2% of the livers. Steatosis, fibrosis, and cancer are highly prevalent in elderly cadavers with diverse causes of death. The prevalence of steatosis and fibrosis is consistent with the data in patients with specific liver diseases. Steatosis alongside fibrosis can accelerate the progression of fibrosis to cirrhosis and ultimately HCC. Though not indicated as the primary cause of death, the liver injury may have compromised hepatic functions and enhanced disease susceptibility, thereby exacerbating the health conditions in this elderly population.

Downregulation of hepatic stellate cell activation by retinol and palmitate mediated by adipose differentiation-related protein (ADRP).

Hepatic stellate cells (HSCs) store retinoids and triacylglycerols in cytoplasmic lipid droplets. Two prominent features of HSC activation in liver fibrosis are loss of lipid droplets along with increase of alpha-smooth muscle actin (alpha-SMA), but the link between these responses and HSC activation remains elusive. In non-adipose cells, adipose differentiation-related protein (ADRP) coats lipid droplets and regulates their formation and lipolysis; however its function in HSCs is unknown. Here, we observed, in human liver sections or primary HSC culture, ADRP localization to lipid droplets of HSCs, and reduced staining coincident with loss of lipid droplets in liver fibrosis and in culture-activated HSCs, consistent with HSC activation. In the LX-2 human immortalized HSCs, with scant lipid droplets and features of activated HSCs, we found that the upregulation of ADRP mRNA by palmitate is potentiated by retinol, accompanied by increased ADRP protein, generation of retinyl palmitate, and lipid droplet formation. ADRP induction also led to decreased expression of alpha-SMA mRNA and its protein, while ADRP knockdown with small interfering RNA (siRNA) normalized alpha-SMA expression. Furthermore, ADRP induction by retinol and palmitate resulted in decreased expression of collagen I and matrix metalloproteinase-2 mRNA, fibrogenic genes associated with activated HSCs, while increasing matrix metalloproteinase-1 mRNA; ADRP knockdown with siRNA reversed these changes. Tissue inhibitor of metalloproteinase-1 was not affected. Thus, ADRP upregulation mediated by retinol and palmitate promotes downregulation of HSC activation and is functionally linked to the expression of fibrogenic genes.

Adipose differentiation-related protein is a reliable lipid droplet marker in alcoholic fatty liver of rats.

BACKGROUND: Adipose differentiation-related protein (ADRP) is a lipid droplet-associated protein that coats cytoplasmic lipid droplets. The present study evaluated whether alcohol feeding enhances ADRP expression and whether ADRP is a lipid droplet marker in alcoholic fatty liver of rats. Because medium-chain triglycerides (MCT) reduce alcoholic hepatosteatosis, their effects on ADRP were also evaluated. METHODS: Fatty liver was induced in rats by the consumption of the Lieber-DeCarli alcohol liquid diet with or without replacement of long-chain triglycerides (LCT) by MCT (32% of calories). Immunohistochemical staining for ADRP was performed in formalin-fixed, paraffin-embedded liver sections. ADRP immunostaining was quantified by image analysis. Triacylglycerol was measured chemically. ADRP mRNA and protein were analyzed by real-time polymerase chain reaction and western blot, respectively. Double staining technique was performed to distinguish ADRP from glycogen in hepatocytes. RESULTS: Alcohol feeding for 21 days increased ADRP staining in the centrilobular and mid zonal regions of the liver lobules coincident with fat deposition in the liver. Replacing LCT in the alcohol diet with MCT diminished ADRP immunostaining in parallel with reduced steatosis. MCT also attenuated the up-regulation of ADRP mRNA and protein after alcohol. In steatotic hepatocytes ADRP selectively stained the surface of macrovesicular and microvesicular lipid droplets. ADRP immunostaining quantitatively correlated with hepatic triacylglycerol levels, validating ADRP as a reliable lipid droplet marker. Compared with hematoxylin and eosin stains, ADRP was more sensitive in detecting microvesicular lipid droplets. ADRP immunostaining also distinguished lipid droplets from glycogen, as demonstrated by double staining for ADRP and glycogen. CONCLUSIONS: Alcohol induction of fatty liver enhances ADRP expression and MCT oppose the alcohol effects. ADRP is a reliable and sensitive marker for lipid droplets in alcoholic fatty liver. ADRP immunostaining permits quantification of fatty change in hepatocytes and can be used as an ancillary technique in assessing the efficacy of diets or drugs against hepatosteatosis.

Beneficial effects versus toxicity of medium-chain triacylglycerols in rats with NASH.

BACKGROUND/AIMS: Replacing long-chain triacylglycerols (LCT) with medium-chain triacylglycerols (MCT) reduces alcohol-induced liver injury. Because of the similarity of the pathogenesis of alcohol-induced liver damage and non-alcoholic steatohepatitis (NASH), our aim was to assess whether MCT is also beneficial in NASH. METHODS: We used a rat NASH model in which corn oil (35% of total calories) was isocalorically replaced with MCT. RESULTS: Partial replacement of LCT did not ameliorate hepatic fat accumulation, 4-hydroxynonenal, collagen type I and its mRNA but it increased TNF-alpha and its mRNA (p<0.001). However, in rats given the high-fat diet restricted to 2/3 of the amount they were consuming, these adverse effects decreased, with and without MCT including less liver steatosis and lower triacylglycerols, but without beneficial effects of MCT. When 70% of the fat calories were replaced with MCT with no LCT remaining in the diet, no steatosis developed and hepatic TNF-alpha was low. When all MCT were given with carbohydrates (instead of LCT) hepatic TNF-alpha also decreased (p<0.001). CONCLUSIONS: MCT are not hepatotoxic, provided the diet contains no significant amount of LCT. Total replacement of dietary LCT with MCT fed ad libitum is beneficial whereas partial replacement becomes hepatotoxic, unless the dietary intake is restricted.

Role of medium-chain triglycerides in the alcohol-mediated cytochrome P450 2E1 induction of mitochondria.

BACKGROUND: Chronic alcohol consumption is known to induce cytochrome P450 2E1 (CYP2E1) leading to lipid peroxidation, mitochondrial dysfunction and hepatotoxicity. We showed that replacement of dietary long-chain triglycerides (LCT) by medium-chain triglycerides (MCT) could be protective. We now wondered whether the induction of mitochondrial CYP2E1 plays a role and whether liver injury could be avoided through mitochondrial intervention. METHODS: Rats were fed 4 different isocaloric liquid diets. The control group received our standard dextrin-maltose diet with intake limited to the average consumption of the 3 alcohol groups fed ad libitum the alcohol containing Lieber-DeCarli liquid diet. The fat was either 32% of calories as LCT (alcohol), or 16% as LCT + 16% as MCT (alcohol-MCT 16%), or 32% as MCT only (alcohol-MCT 32%). RESULTS: After 21 days, compared to the controls, the alcohol and both alcohol-MCT groups had a significant increase in mitochondrial CYP2E1 (p < 0.05 for both). As shown before, the same was found for the microsomal CYP2E1. When MCT replaced all the fat, like in the alcohol-MCT 32% group, CYP2E1 was significantly reduced by 40% in mitochondria (p < 0.05) and 30% in microsomes (p < 0.01). In mitochondria, 4-hydroxynonenal (4-HNE), a parameter of oxidative stress, paralleled CYP2E1. Compared to controls, alcohol and alcohol-MCT 16% significantly raised mitochondrial 4-HNE (p < 0.001), whereas the alcohol-MCT 32% diet brought it down to control levels (p < 0.001). Mitochondrial reduced glutathione (GSH) was also significantly lowered by alcohol consumption (p < 0.05), and it increased to almost normal levels with alcohol-MCT 32% (p = 0.006). These changes in the mitochondria reflected the reduction observed in total liver in which alcohol-MCT 32% decreased the alcohol-induced steatosis with a diminution of triglycerides (p < 0.001) and of the pro-inflammatory cytokine tumor necrosis factor-alpha (p < 0.001). CONCLUSION: Mitochondria participate in the induction of CYP2E1 by alcohol and contribute to lipid peroxidation and GSH depletion. Thus, lipid composition of the diet is an important determinant for the beneficial effect of MCT, with a diet containing a mixture of LCT/MCT being ineffective.

Leptin represses matrix metalloproteinase-1 gene expression in LX2 human hepatic stellate cells.

BACKGROUND/AIMS: Collagen accumulation in liver fibrosis is due in part to decreased expression of matrix metalloproteinase (MMP)-1 relative to TIMP-1. LX-2 hepatic stellate cells produce increased amounts of collagen and tissue inhibitor of metalloproteinase (TIMP)-1 in response to leptin. The effect of leptin on MMP-1 production has not been reported. METHODS: LX-2 cells were treated with leptin with or without inhibitors. We determined: phosphorylation of Janus kinase (JAK) 1 and -2, signal transducer and activator of transcription (STAT)3 and -5, extracellular signal-regulated kinase (ERK)1/2 and p38 by Western blot; H2O2 concentration by a colorimetric method; MMP-1 mRNA levels and stability by Northern blot; MMP-1 promoter activity as well as pro-MMP-1 by ELISA; and active MMP-1 by fluorescence. RESULTS: LX-2 cells constitutively expressed the MMP-1 gene and leptin repressed the basal level of MMP-1 mRNA and its promoter activity. The repression was mediated by JAK/STAT pathway in synergism with JAK-mediated H2O2-dependent ERK1/2 and p38 pathways. ERK1/2 inhibited MMP-1 promoter activity, whereas p38 decreased the message stability, contributing to mRNA down-regulation. Inhibition of MMP-1 gene diminished secreted pro-MMP-1 and active MMP-1. CONCLUSIONS: Leptin represses MMP-1 gene expression via the synergistic actions of the JAK/STAT pathway and JAK-mediated H2O2-dependent ERK1/2 and p38 pathways.

The Combination of S-adenosylmethionine and Dilinoleoylphosphatidylcholine Attenuates Non-alcoholic Steatohepatitis Produced in Rats by a High-Fat Diet.

In the pathogenesis of non-alcoholic steatohepatitis (NASH), oxidative stress resulting from free radicals generated by cytochrome P4502E1 (CYP2E1) plays a major role suggesting the importance of antioxidants. The objective of this study was to assess in a high-fat diet (HF) rat model the effects of the combination of s-adenosylmethionine (SAMe) plus dilinoleoylphosphatidylcholine (DLPC) in the treatment of NASH. To test the hypothesis that these two antioxidants are beneficial in NASH, male Sprague-Dawley rats were fed five different diets for six weeks: control, HF diet and HF plus SAMe and DLPC or their combination. As expected, the HF diet significantly increased hepatic triacylglycerols and CYP2E1 levels. However, only the combination diet opposed this effect, consistent with different actions of the two antioxidants. Next, 24 additional rats divided in two groups were fed the HF or the HF+SAMe+DLPC diets for 3 weeks. Dietary intake was similar, but liver triacylglycerols dropped from 76.1+/-6.8 to 49.4+/-3.5 mg/g (p=0.002) and hepatic CYP2E1 mRNA decreased after treatment (p=0.01) with a trend for less CYP2E1 protein. This was accompanied by a 41% reduction of hepatic 4-hydroxynonenal (4-HNE) (p=0.008), reflecting control of oxidative stress. Furthermore, the hepatic inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) mRNA and TNF-alpha protein decreased (p=0.05 and p=0.01 respectively) with attenuation of alpha1(I) procollagen mRNA and type I collagen levels (p=0.01 and p=0.02, respectively). We concluded that the combination SAMe+DLPC might be beneficial in NASH by reducing oxidative stress and associated liver injury.

DLPC and SAMe prevent alpha1(I) collagen mRNA up-regulation in human hepatic stellate cells, whether caused by leptin or menadione.

We previously reported that the combination of dilinoleoylphosphatidylcholine (DLPC) and S-adenosylmethionine (SAMe), which have antioxidant properties and antifibrogenic actions, prevented leptin-stimulated tissue inhibitor of metalloproteinase (TIMP)-1 production in hepatic stellate cells (HSCs) by inhibiting H2O2-mediated signal transduction. We now show that DLPC and SAMe inhibit alpha1(I) collagen mRNA expression induced by leptin or menadione in LX-2 human HSCs. We found that DLPC and SAMe prevent H2O2 generation and restore reduced glutathione (GSH) depletion whether caused by leptin or menadione. Blocking H2O2 signaling through ERK1/2 and p38 pathways resulted in a complete inhibition of leptin or menadione-induced alpha1(I) collagen mRNA. The inhibition of collagen mRNA by DLPC and SAMe combined is at least two times more effective than that by DLPC or SAMe alone. In conjunction with the prevention of TIMP-1 production, the ability of DLPC and SAMe to inhibit alpha1(I) collagen mRNA expression provides a mechanistic basis for these innocuous compounds in the prevention of hepatic fibrosis, because enhanced TIMP-1 and collagen productions are associated with hepatic fibrogenesis and their attenuation may diminish fibrosis.

DLPC and SAMe combined prevent leptin-stimulated TIMP-1 production in LX-2 human hepatic stellate cells by inhibiting HO-mediated signal transduction.

BACKGROUND/AIMS: Both dilinoleoylphosphatidylcholine (DLPC) and S-adenosylmethionine (SAMe) have antioxidant properties and antifibrogenic actions. Because H2O2 mediates signal transduction-stimulating liver fibrogenesis, we investigated whether DLPC and SAMe attenuate the production of tissue inhibitor of metalloproteinase (TIMP)-1 by inhibiting H2O2 formation. METHODS: LX-2 human hepatic stellate cells were treated with leptin with or without DLPC, SAMe or various inhibitors. RESULTS: Leptin-stimulated TIMP-1 mRNA and its protein were diminished by DLPC or SAMe alone, and the response was fully prevented by the combination of DLPC and SAMe. H2O2 was increased while glutathione was decreased; these changes were prevented by AG490, suggesting a Janus kinases (JAK)-mediated process. Up-regulation of leptin receptor and activation of JAK1 and 2 were not affected by DLPC+SAMe, whereas phosphorylation of ERK1/2 and p38 was blocked by DLPC+SAMe or catalase, suggesting an H2O2-dependent mechanism. These treatments also suppressed leptin-stimulated TIMP-1 promoter activity and decreased TIMP-1 mRNA stability, contributing to TIMP-1 mRNA down-regulation. PD098059, an ERK1/2 inhibitor, suppressed TIMP-1 promoter activity, whereas SB203580, a p38 inhibitor, decreased TIMP-1 message stability; both resulted in a partial reduction of TIMP-1 mRNA. CONCLUSION: As decreased TIMP-1 production may enhance collagen deposition, the combined administration of DLPC+SAMe should be considered for the prevention of H2O2-mediated signaling and the resulting fibrosis.