Hepatic fatty acid composition differs between chronic hepatitis C patients with and without steatosis

Time course of western diet (WD) induced nonalcoholic steatohepatitis (NASH) in female and male Ldlr-/- mice

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a global health problem. Identification of factors contributing to the onset and progression of NAFLD have the potential to direct novel strategies to combat NAFLD.

METHODS

We examined the time course of western diet (WD)-induced NAFLD and its progression to nonalcoholic steatohepatitis (NASH) in age-matched female and male Ldlr-/- mice, with time-points at 1, 4, 8, 20 and 40 weeks on the WD. Controls included Ldlr-/- mice maintained on a purified low-fat diet (LFD) for 1 and 40 weeks. The approach included quantitation of anthropometric, plasma and liver markers of disease, plus hepatic histology, lipids, oxylipins, gene expression and selected metabolites.

RESULTS

One week of feeding the WD caused a significant reduction in hepatic essential fatty acids (EFAs: 18:2, ω6, 18:3, ω3) which preceded the decline in many C20-22 ω3 and ω6 polyunsaturated fatty acids (PUFA) and PUFA-derived oxylipins after 4 weeks on the WD. In addition, expression of hepatic inflammation markers (CD40, CD44, Mcp1, Nlrp3, TLR2, TLR4, Trem2) increased significantly in both female & male mice after one week on the WD. These markers continued to increase over the 40-week WD feeding study. WD effects on hepatic EFA and inflammation preceded all significant WD-induced changes in body weight, insulin resistance (HOMA-IR), oxidative stress status (GSH/GSSG ratio) and histological and gene expression markers of macrosteatosis, extracellular matrix remodeling and fibrosis.

CONCLUSIONS

Our findings establish that feeding Ldlr-/- mice the WD rapidly lowered hepatic EFAs and induced key inflammatory markers linked to NASH. Since EFAs have an established role in inflammation and hepatic inflammation plays a major role in NASH, we suggest that early clinical assessment of EFA status and correcting EFA deficiencies may be useful in reducing NASH severity.

Nonalcoholic Fatty Liver Disease and Omega-3 Fatty Acids: Mechanisms and Clinical Use

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic fatty liver disease worldwide, particularly in obese and type 2 diabetic individuals. Currently, there are no therapies for NAFLD that have been approved by the US Food and Drug Administration. Herein, we examine the rationale for using ω3 polyunsaturated fatty acids (PUFAs) in NAFLD therapy. This focus is based on the finding that NAFLD severity is associated with a reduction of hepatic C20-22 ω3 PUFAs. Because C20-22 ω3 PUFAs are pleiotropic regulators of cell function, loss of C20-22 ω3 PUFAs has the potential to significantly impact hepatic function. We describe NAFLD prevalence and pathophysiology as well as current NAFLD therapies. We also present evidence from clinical and preclinical studies that evaluated the capacity of C20-22 ω3 PUFAs to treat NAFLD. Given the clinical and preclinical evidence, dietary C20-22 ω3 PUFA supplementation has the potential to decrease human NAFLD severity by reducing hepatosteatosis and liver injury.

Western diet consumption through early life induces microvesicular hepatic steatosis in association with an altered metabolome in low birth weight Guinea pigs

Uteroplacental insufficiency-induced low birth weight (LBW) and postnatal high saturated fat/high sucrose-fructose diet (Western Diet, WD) consumption have been independently associated with the development of hepatic steatosis, while their additive effect on fatty acid, acylcarnitine and amino acid profiles in early adulthood have not been widely reported. We employed LBW, generated via uterine artery ablation, and normal birth weight (NBW) male guinea pigs fed either a WD or control diet (CD) from weaning to postnatal day 150 (early adulthood). Hepatic steatosis was absent in CD-fed offspring, while NBW/WD offspring displayed macrovesicular steatosis and LBW/WD offspring exhibited microvesicular steatosis, both occurring in a lean phenotype. Life-long consumption of the WD, irrespective of birth weight, was associated with an increase in hepatic medium- and long-chain saturated fatty acids, monounsaturated fatty acids, acylcarnitines, reduced oxidative phosphorylation complex III activity and polyunsaturated fatty acids, and molecular evidence of disrupted hepatic insulin signaling. In NBW/WD, hepatic C15:1 and C16:1n-6 fatty acids in phospholipids, C16, C18 and C18:1 acylcarnitines, concentrations of aspartate, phenylalanine, tyrosine and tryptophan and expression of carnitine palmitoyltransferase 1 alpha (CPT1α) and uncoupling protein 2 (UCP2) genes were elevated compared to LBW/WD livers. Our results suggest that LBW and life-long WD combined are influential in promoting hepatic microvesicular steatosis in conjunction with a specific mitochondrial gene expression and metabolomic profile in early adulthood.

Omega-3 polyunsaturated fatty acids as a treatment strategy for nonalcoholic fatty liver disease

Obese and type 2 diabetic (T2DM) patients have a high prevalence of nonalcoholic fatty liver disease (NAFLD). NAFLD is a continuum of chronic liver diseases ranging from benign hepatosteatosis to nonalcoholic steatohepatitis (NASH), cirrhosis and primary hepatocellular cancer (HCC). Because of its strong association with the obesity epidemic, NAFLD is rapidly becoming a major public health concern worldwide. Surprisingly, there are no FDA approved NAFLD therapies; and current therapies focus on the co-morbidities associated with NAFLD, namely, obesity, hyperglycemia, dyslipidemia, and hypertension. The goal of this review is to provide background on the disease process, discuss human studies and preclinical models that have examined treatment options. We also provide an in-depth rationale for the use of dietary ω3 polyunsaturated fatty acid (ω3 PUFA) supplements as a treatment option for NAFLD. This focus is based on recent studies indicating that NASH patients and preclinical mouse models of NASH have low levels of hepatic C_20-22 ω3 PUFA. This decline in hepatic PUFA may account for the major phenotypic features associated with NASH, including steatosis, inflammation and fibrosis. Finally, our discussion will address the strengths and limitations of ω3 PUFA supplements use in NAFLD therapy.

Docosahexaenoic acid blocks progression of western diet-induced nonalcoholic steatohepatitis in obese Ldlr-/- mice

Background

Nonalcoholic fatty liver disease (NAFLD) is a major public health concern in western societies. Nonalcoholic steatohepatitis (NASH), the progressive form of NAFLD, is characterized by hepatic steatosis, inflammation, oxidative stress and fibrosis. NASH is a risk factor for cirrhosis and hepatocellular carcinoma. NASH is predicted to be the leading cause of liver transplants by 2020. Despite this growing public health concern, there remain no Food and Drug Administration (FDA) approved NASH treatments. Using Ldlr^-/- mice as a preclinical model of western diet (WD)-induced NASH, we previously established that dietary supplementation with docosahexaenoic acid (DHA, 22:6,ω3) attenuated WD-induced NASH in a prevention study. Herein, we evaluated the capacity of DHA supplementation of the WD and a low fat diet to fully reverse NASH in mice with pre-existing disease.

Methods

Ldlr^-/- mice fed the WD for 22 wks developed metabolic syndrome (MetS) and a severe NASH phenotype, including obesity, dyslipidemia, hyperglycemia, hepatic steatosis, inflammation, fibrosis and low hepatic polyunsaturated fatty acid (PUFA) content. These mice were randomized to 5 groups: a baseline group (WDB, sacrificed at 22 wks) and 4 treatments: 1) WD + olive oil (WDO); 2) WD + DHA (WDD); 3) returned to chow + olive oil (WDChO); or 4) returned to chow + DHA (WDChD). The four treatment groups were maintained on their respective diets for 8 wks. An additional group was maintained on standard laboratory chow (Reference Diet, RD) for the 30-wk duration of the study.

Results

When compared to the WDB group, the WDO group displayed increased hepatic expression of genes linked to inflammation (Opn, Il1rn, Gdf15), hepatic fibrosis (collagen staining, Col1A1, Thbs2, Lox) reflecting disease progression. Mice in the WDD group, in contrast, had increased hepatic C_20-22 ω3 PUFA and no evidence of NASH progression. MetS and NASH markers in the WDChO or WDChD groups were significantly attenuated and marginally different from the RD group, reflecting disease remission.

Conclusion

While these studies establish that DHA supplementation of the WD blocks WD-induced NASH progression, DHA alone does not promote full remission of diet-induced MetS or NASH.

Serum lipid profile as a marker of liver impairment in hepatitis B Cirrhosis patients

BACKGROUND

Chronic HBV infection is a major cause of Cirrhosis and an important risk factor to develop hepatocellular carcinoma. The study is conducted to find out the changes in the lipid metabolism of HBV-cirrhosis patients.

METHODS

In the present study, serum lipid profiles of patients with HBV-cirrhosis were assessed by utilizing micro-lab and gas chromatography, while risk factors for transmission of HBV-cirrhosis studied through the standard questionnaire.

RESULTS

The epidemiological and etiological risk factors strongly associated with HBV-cirrhosis patients compared to controls, included as family history, shave from the barber, blood transfusion (without proper screening), mutual sharing of household contents, positive surgery history, and dental treatment. The HBV-cirrhosis patients have significantly lower level (p < 0.001) of lipid profile including total cholesterol (96.65 mg/dl), TAG (82.85 mg/dl), VLDL-C (16.57 mg/dl), LDL-C (68.27 mg/dl), HDL-C (27 mg/dl) and total lipid (424.76 mg/dl) in comparison to controls, indicating hypolipidemia in patients. The MELD score indicated mild prognostic values of the hepatic function for the study group. The result of total fatty acid composition of HBV-cirrhotic patients with comparison of control subjects reveals that palmitic (24.54 g/100 g) and palmitoleic acid (4.65 g/100 g) were significantly (p < 0.05) higher whereas eicosatrienoic (0.09 g/100 g), arachidonic (3.57 g/100 g), linoleic (22.75 g/100 g) and α-linolenic acid (0.12 g/100 g) were significantly lower. Marker for stearoyl-CoA desaturase (SCD = ∆9-desaturase) activity i.e. palmitoleic: palmitic (0.2) and oleic: stearic acid (1.5) ratios, originated higher in HBV-cirrhotic patients, while PUFA: SFA (0.6) was lower in HBV-cirrhosis patients as compared with control subjects. The serum SFA and MUFA were increased while PUFA were reduced in both total and free form.

CONCLUSION

Present study concluded that hypolipidemia observed in HBV-cirrhosis patients, MELD were found to be independent predictors of survival and alteration in fatty acid composition, possibly due to impairment in fatty acid metabolism by enzymatic elongation and desaturation.

Plasma phospholipids and fatty acid composition differ between liver biopsy-proven nonalcoholic fatty liver disease and healthy subjects

Background:

There is growing evidence that nonalcoholic fatty liver disease (NAFLD) is associated with perturbations in liver lipid metabolism. Liver phospholipid and fatty acid composition have been shown to be altered in NAFLD. However, detailed profiles of circulating lipids in the pathogenesis of NAFLD are lacking.

Objective:

Therefore, the objective of the present study was to examine circulating lipids and potential mechanisms related to hepatic gene expression between liver biopsy-proven simple steatosis (SS), nonalcoholic steatohepatitis (NASH) and healthy subjects.

Subjects:

Plasma phospholipid and fatty acid composition were determined in 31 healthy living liver donors as healthy controls (HC), 26 patients with simple hepatic steatosis (SS) and 20 with progressive NASH. Hepatic gene expression was analyzed by Illumina microarray in a subset of 22 HC, 16 SS and 14 NASH.

Results:

Concentrations of phosphatidylethanolamine (PE) increased relative to disease progression, HC<SS<NASH (170<210<250 μg ml⁻¹), and was significantly different (P<0.05) between HC and NASH. Circulating phosphatidylserine (PS) and phosphatidylinositol were higher in SS and NASH compared with HC (P<0.05), but there was no difference between SS and NASH. Fatty acid composition of phospholipids was also remodeled. In particular, docosahexaenoic and arachidonic acid were higher (P<0.05) in SS and NASH relative to HC in PS. Differentially expressed hepatic genes included ETNK1 and PLSCR1 that are involved in PE synthesis and PS transport, respectively.

Conclusions:

The present study demonstrates that there is a disruption in phospholipid metabolism that is present in SS, but more pronounced in NASH. Intervention studies targeted at lipid metabolism could benefit SS and NASH.

A comparative study of serum lipid contents in pre and post IFN-alpha treated acute hepatitis C patients

BACKGROUND

To study the effect of Interferon (INF) alpha-2b therapy on the serum lipids and fatty acid (FA) level in pre and post treated hepatitis C (HCV) patients.

METHODS

Fifty samples were collected from pre and post treated patients along with age and gender matched controls. After separating serum, lipid contents were analyzed by microlab and gas chromatography.

RESULTS

The hepatitis C infection results in hypolipidemia with reduced level of triglyceride (113 mg/dl), high density lipoprotein (37.1 mg/dl), low density lipoprotein (74.3 mg/dl), cholesterol (149.9 mg/dl) that increase the infection resolution and after the IFN treatment, the lipid profile of the patients were increased. The myristic (2.8 g/100 g) and palmitic acids (26.6 g/100 g) were significantly higher while linoleic acid (20.94 g/100 g) was significantly lower in HCV patients. The higher oleic: stearic (1.4) and palmitoleic: palmitic acid (0.2) ratios were detected in HCV patients, showing enhanced stearoyl-CoA desaturase activity. The levels of serum saturated (44.9 g/100 g) and monounsaturated FA's (26.98 g/100 g) were higher while polyunsaturated FA's (25.9 g/100 g) were found lower in HCV patients in comparison of controls (40.1; 25.01; 33.44 g/100 g respectively). An inverse correlation was found HCV RNA viral load and PUFA (R(2) = 0.4555). Elevated levels of serum saturated free FA (45.7 g/100 g) in HCV patients indicates stimulated lipoapoptosis.

CONCLUSION

The present study conclude that serum PUFA level was lower in HCV patients, hence PUFA may provide synergistic antiviral effects when given as a food supplement during the INF based anti- HCV therapy.

Suppressive Role of PPARγ-Regulated Endothelial Nitric Oxide Synthase in Adipocyte Lipolysis

Introduction

Metabolic syndrome causes insulin resistance and is associated with risk factor clustering, thereby increasing the risk of atherosclerosis. Recently, endothelial nitric oxide synthase deficient (eNOS-/-) mice have been reported to show metabolic disorders. Interestingly, eNOS has also been reported to be expressed in non-endothelial cells including adipocytes, but the functions of eNOS in adipocytes remain unclear.

Methods and Results

The eNOS expression was induced with adipocyte differentiation and inhibition of eNOS/NO enhanced lipolysis in vitro and in vivo. Furthermore, the administration of a high fat diet (HFD) was able to induce non-alcoholic steatohepatitis (NASH) in eNOS-/- mice but not in wild type mice. A PPARγ antagonist increased eNOS expression in adipocytes and suppressed HFD-induced fatty liver changes.

Conclusions

eNOS-/- mice induce NASH development, and these findings provide new insights into the therapeutic approach for fatty liver disease and related disorders.

Reduction in the desaturation capacity of the liver in mice subjected to high fat diet: Relation to LCPUFA depletion in liver and extrahepatic tissues

α-Linolenic (ALA) and linoleic (LA) acids are precursors of long chain polyunsaturated fatty acids (LCPUFAs), FAs with important biochemical and physiological functions. In this process, desaturation reactions catalyzed by Δ5- and Δ6-desaturase play a major role, enzymes that are subjected to hormonal and dietary regulation. The aim of this study was to assess the influence of a high fat diet (HFD) on activity of liver Δ5 and Δ6 desaturases, in relation to LCPUFA composition in liver and extrahepatic tissues. Male C57BL/6J mice received control diet (CD) (10% fat, 20% protein and 70% carbohydrate) or high fat diet (HFD) (60% fat, 20% protein, and 20% carbohydrate) for 12 weeks. After this time, blood and liver samples were taken for metabolic, morphologic, inflammatory, oxidative stress and desaturase activity assessment, besides FA phospholipid analysis in erythrocytes, heart, adipose tissue and brain. HFD significantly increased hepatic total fat, triacylglycerides and free FA content with macrovesicular steatosis and oxidative stress enhancement, concomitantly with higher fasting serum glucose and insulin levels, HOMA, and serum cholesterol, triacylglycerols, TNF-α, and IL-6. Diminution in liver Δ5- and Δ6-desaturase activities and LCPUFA depletion were induced by HFD, the later finding being also observed in extrahepatic tissues. In conclusion, HFD-induced reduction in the bioavailability of liver LCPUFA is associated with defective desaturation of ALA and LA, with Δ5- and Δ6-desaturase activities being correlated with insulin resistance development. Data analyzed point to the liver as a major organ responsible for extrahepatic LCPUFA homeostasis, which is markedly deranged by HFD.

Small molecule glucokinase activators disturb lipid homeostasis and induce fatty liver in rodents: a warning for therapeutic applications in humans

BACKGROUND AND PURPOSE

Small-molecule glucokinase activators (GKAs) are currently being investigated as therapeutic options for the treatment of type 2 diabetes (T2D). Because liver overexpression of glucokinase is thought to be associated with altered lipid profiles, this study aimed at assessing the potential lipogenic risks linked to oral GKA administration.

EXPERIMENTAL APPROACH

Nine GKA candidates were qualified for their ability to activate recombinant glucokinase and to stimulate glycogen synthesis in rat hepatocytes and insulin secretion in rat INS-1E cells. In vivo activity was monitored by plasma glucose and HbA1c measurements after oral administration in rodents. Risk-associated effects were assessed by measuring hepatic and plasma triglycerides and free fatty acids, as well as plasma aminotransferases, and alkaline phosphatase.

KEY RESULTS

GKAs, while efficiently decreasing glycaemia in acute conditions and HbA1c levels after chronic administration in hyperglycemic db/db mice, were potent inducers of hepatic steatosis. This adverse outcome appeared as soon as 4 days after daily oral administration at pharmacological doses and was not transient. GKA treatment similarly increased hepatic triglycerides in diabetic and normoglycaemic rats, together with a pattern of metabolic phenotypes including different combinations of increased plasma triglycerides, free fatty acids, alanine and aspartyl aminotransferases, and alkaline phosphatase. GKAs belonging to three distinct structural families induced hepatic steatosis in db/db mice, arguing in favour of a target-mediated, rather than a chemical class-mediated, effect.

CONCLUSION AND IMPLICATIONS

Given the risks associated with fatty liver disease in the general population and furthermore in patients with T2D, these findings represent a serious warning for the use of GKAs in humans.

LINKED ARTICLE

This article is commented on by Rees and Gloyn, pp. 335-338 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2012.02201.x.

In vivo (1)H-MRS hepatic lipid profiling in nonalcoholic fatty liver disease: an animal study at 9.4 T

The applicability of the in vivo proton magnetic resonance spectroscopy hepatic lipid profiling (MR-HLP) technique in nonalcoholic fatty liver disease was investigated. Using magnetic resonance spectroscopy, the relative fractions of diunsaturated (fdi), monounsaturated (fmono), and saturated (fsat) fatty acids as well as total hepatic lipid content were estimated in the livers of 8 control and 23 CCl4-treated rats at 9.4 T. The mean steatosis, necrosis, inflammation, and fibrosis scores of the treated group were all significantly higher than those of the control group (P < 0.01). There was a strong correlation between the histopathologic parameters and the MR-HLP parameters (r = 0.775, P < 0.01) where both steatosis and fibrosis are positively correlated with fmono and negatively correlated with fdi. Both necrosis and inflammation, however, were not correlated with any of the MR-HLP parameters. Hepatic lipid composition appears to be changed in association with the severity of steatosis and fibrosis in nonalcoholic fatty liver disease, and these changes can be depicted in vivo by using the MR-HLP method at 9.4 T. Thus, while it may not likely be that MR-HLP helps differentiate between steatohepatitis in its early stages and simple steatosis, these findings altogether are in support of potential applicability of in vivo MR-HLP at high field in nonalcoholic fatty liver disease.

Inhibition of MEK/ERK1/2 Signaling Affects the Fatty Acid Composition of HepG2 Human Hepatic Cell Line

INTRODUCTION

The extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase pathway, also known as the MEK/ERK1/2 kinase cascade, has recently been implicated in the regulation of lipid metabolism and fatty liver disease. However, its functional effect on cellular fatty acid composition is unknown. Herein, we examined the effect of a pharmacological inhibitor of MEK, the upstream kinase activator of ERK1/2, on fatty acid composition of hepatocellular carcinoma cell line HepG2.

METHODS

HepG2 cells cultured in RPMI-1640 were exposed to the commonly used ERK1/2 pathway inhibitor PD98059 and were investigated with respect to fatty acid composition by gas-liquid chromatography.

RESULTS

Exposure of cells to the ERK1/2 pathway inhibitor induced an increase in monounsaturated fatty acids and the fatty acid desaturation index and a decrease in polyunsaturated fatty acid content. Specifically, we showed a significant increase of oleic acid (18:1n-9; +29%, P=0.003) and arachidonic acid (20:4n-6)/linoleic acid (18:2n-6) ratio (3.5-fold; P<0.001) in HepG2 cells.

CONCLUSION

Cellular fatty acid composition of HepG2 cells appeared to be differentially regulated by ERK1/2 pathway, thus suggesting related metabolic pathways as potential mediators of the effects of ERK1/2 signaling on hepatic fatty acid composition.

Relationships between hepatic stearoyl-CoA desaturase-1 activity and mRNA expression with liver fat content in humans

Stearoyl-CoA desaturase-1 (SCD1) has gained much interest as a future drug target to treat fatty liver and its consequences. However, there are few and inconsistent human data about expression and activity of this important enzyme. We investigated activity and expression of SCD1 and their relationships with liver fat (LF) content in human liver samples. Fifty subjects undergoing liver surgery were studied. SCD1 activity was estimated from the ratio of oleate (C18:1) to stearate (C18:0) within lipid subfractions. Furthermore, SCD1 mRNA expression and LF content were measured. Similarly to previous studies, we observed a strong positive correlation between LF content and the C18:1/C18:0 ratio in the combined fatty acid (FA) fractions (r = 0.96, P < 0.0001), which could be interpreted as higher SCD1 activity with increasing LF. However, hepatic SCD1 mRNA expression did not correlate with LF (r = 0.16, P = 0.13). To solve these conflicting data, we analyzed the FA composition of hepatic lipid subfractions. With increasing LF content the amount of FAs from the triglyceride (TG) fraction increased (r = 0.96, P < 0.0001), whereas the FAs from the phospholipid (PL) fraction remained unchanged (r = -0.17, P = 0.19). Of these two major lipid fractions, the C18:1/C18:0 ratio in TG was 16-fold higher than in PL. Supporting the SCD1 mRNA expression data, the C18:1/C18:0 ratio of the TG or PL fraction did not correlate with LF (r = 0.26, P = 0.12 and r = 0.08, P = 0.29). We provide novel information that SCD1 activity and mRNA expression appear not to be elevated in subjects with high LF content. We suggest that the FA composition of lipid subclasses, rather than of mixed lipids, should be analyzed to estimate SCD1 activity.

Distribution of omega-3 fatty acids in tissues of rabbits fed a flaxseed-supplemented diet

Diets rich in omega-3 polyunsaturated fatty acids are associated with decreased incidences of cardiovascular disease. The extent of incorporation and distribution of these beneficial fats into body tissues is uncertain. Rabbits were fed regular rabbit chow or a diet containing 10% ground flaxseed that is highly enriched with the omega-3 polyunsaturated fatty acid alpha-linolenic acid (ALA). The high-flaxseed diet resulted in an incorporation of ALA in all tissues, but mostly in the heart and liver with little in the brain. Docosahexaenoic and eicosapentaenoic acid levels were also selectively increased in some tissues, and the effects were not as large as ALA. Arachidonic acid and the ratio of omega-6/omega-3 fatty acids were decreased in all tissues obtained from the flax-supplemented group. Consumption of dietary flaxseed appears to be an effective means to increase ALA content in body tissues, but the degree will depend upon the tissues examined.