Differential effect of oleic and palmitic acid on lipid accumulation and apoptosis in cultured hepatocytes.

BACKGROUND AND AIM: Studies have shown monounsaturated oleic acid to be less toxic than palmitic acid and to prevent/attenuate palmitic acid hepatocites toxicity in steatosis models in vitro. However, to what degree these effects are mediated by steatosis extent is unknown. METHODS: We evaluated whether steatosis per se is associated with hepatocytes apoptosis and determined the role of oleic and palmitic acid, the most abundant fatty acids in western diets, on triglyceride accumulation and apoptosis in an in vitro model of steatosis induced in three hepatocytic cell lines (HepG2, HuH7, WRL68). The impact of incubation for 24 h with oleic (0.66 and 1.32 mM) and palmitic acid (0.33 and 0.66 mM), alone or combined (molar ratio 2 : 1) on steatosis, apoptosis, and insulin signalling, was evaluated. RESULTS: Concurrent with PPARgamma and SREBP-1 gene activation, steatosis extent was larger when cells were treated with oleic than with palmitic acid; the latter fatty acid was associated with increased PPARalpha expression. Cell apoptosis was inversely proportional to steatosis deposition. Moreover, palmitic, but not oleic acid, impaired insulin signalling. Despite the higher amount of fat resulting from incubation of the two fatty acids combined, the apoptosis rate and impaired insulin signalling were lower than in cells treated with palmitic acid alone, indicating a protective effect of oleic acid. CONCLUSIONS: Oleic acid is more steatogenic but less apoptotic than palmitic acid in hepatocityc cell cultures. These data may provide a biological basis for clinical findings on dietary patterns and pathogenetic models of nonalcoholic fatty liver disease.

In vivo degradation of cholesterol to bile acids is reduced in patients receiving parenteral nutrition.

BACKGROUND: Artificial nutrition is frequently associated with hepatobiliary complications, probably due to the inherent derangement of the gastrointestinal tract physiology. Alterations of hepatic lipid metabolism are likely to be involved. The aim of the present study was to investigate the effect of artificial nutrition on bile acid production, a key event in cholesterol homeostasis, in humans. PATIENTS AND METHODS: Eleven patients receiving artificial nutrition, either parenteral nutrition (PN; n = 6) or enteral nutrition (EN; n = 5) with no previous history of liver disease, underwent analysis of cholesterol 7α-hydroxylation rates in vivo, a measure of bile acid formation, by isotope release analysis after intravenous injection of [7α-(3)H]cholesterol. The results were compared with those obtained in a population of 16 age-matched control subjects. RESULTS: Hydroxylation rates were lower in patients with artificial nutrition (PN: 94 ± 13 mg/d; EN: 230 ± 39 mg/d, mean ± SEM) when compared with controls (385 ± 47 mg/d) (P < .01, 1-way analysis of variance). In a patient receiving EN, hydroxylation rates increased 3.5-fold after treatment with the cholecystokinin analogue ceruletide (20 µg bid for 2 weeks intramuscularly). Serum lathosterol-to-cholesterol ratio, a marker of cholesterol synthesis, was also significantly reduced in artificial nutrition, whereas serum levels of fibroblast growth factor 19 (FGF19) were increased. CONCLUSION: In vivo 7α-hydroxylation is suppressed in artificial nutrition, particularly in PN. The finding associates with reduced cholesterol production, possibly as a metabolic consequence. The data suggest a regulatory role of gastrointestinal hormones and FGF19 on bile acid production and might suggest a pathophysiological basis for some common complications of artificial nutrition, such as gallstone disease and cholestasis.

ABCB4 and ABCB11 mutations in intrahepatic cholestasis of pregnancy in an Italian population.

BACKGROUND: Genetic alterations in the ATP-binding cassette subfamily B member 4 (ABCB4) and ATP-binding cassette subfamily B member 11 (ABCB11) have been associated to the onset of intrahepatic cholestasis of pregnancy (ICP) in predisposed women. AIMS: To identify new and/or frequent ABCB4 and ABCB11 genes variants in a cohort of Italian patients with ICP and to evaluate the possible pathogenetic role for the novel mutations identified. METHODS: DNA of 33 unrelated Italian women with obstetric cholestasis were screened for mutations in the entire coding sequence of ABCB4 and ABCB11 genes. Polymerase chain reaction and automated sequencing was performed on the 27 coding exons of both genes. RESULTS: Genotyping revealed 11 mutations, 5 of whom were novel variants: 2 localized on ABCB4 (p.I587DfsX603, p.I738LfsX744) and 3 on ABCB11 (p.V284D, p.Q558H, p.P731S). The most severe phenotypes were associated with the variants p.I587DfsX603, p.I738LfsX744 and p.V284D. Moreover, the already described mutation p.N510S found in ABCB4 seems to be strictly involved in the onset of ICP in that particular patient. CONCLUSIONS: Our data support the hypothesis of a significant involvement of ABCB4 mutations in the onset of ICP, but also confirm an important role for ABCB11 mutations in increasing the susceptibility to cholestasis of pregnancy.

Is nonalcoholic steatohepatitis associated with a high-though-normal thyroid stimulating hormone level and lower cholesterol levels?

Hypothyroidism is associated with the risk of development of the metabolic syndrome (MS) and hypercholesterolemia. Direct evidence that hypothyroidism might be associated with advanced chronic liver disease via nonalcoholic steatohepatitis (NASH) is limited. We studied the relationship between thyroid hormones, thyroid stimulating hormone (TSH), cholesterol, and NASH. In consecutive euthyroid patients with biopsy-proven nonalcoholic fatty liver disease, TSH and thyroid hormone (FT3 and FT4) concentrations were compared in 25 patients with steatosis and 44 non-cirrhotic NASH patients featuring concurrent ballooning, lobular inflammation and steatosis. The MS was diagnosed according to ATP III criteria. A meta-analysis of previously published studies was performed to evaluate whether NASH, compared to simple steatosis, is associated with lower cholesterol levels. At univariate analysis, compared to those with steatosis, patients with NASH have a wider waist, elevated levels of BMI, ALT, AST, fasting insulin, HOMA-IR, ferritin, TSH and a lower serum cholesterol. At stepwise multivariable logistic regression analysis, the independent predictors of NASH are high HOMA and TSH and lower total cholesterol (Model 1); MS and high TSH (Model 2). At meta-analysis, serum total cholesterol levels are significantly lower in predominantly non-cirrhotic NASH than in simple steatosis. This study provides cross-sectional and meta-analytic evidence that, in euthyroid patients, high-though-normal TSH values are independently associated with NASH. Further work is needed to ascertain the role, if any, of lower cholesterol serum levels in assisting in the diagnosis of NASH.

Effects of bile duct ligation and cholic acid treatment on fatty liver in two rat models of non-alcoholic fatty liver disease.

BACKGROUND: Non-alcoholic fatty liver disease, one of the most prevalent liver disorders in Western countries, is characterized by hepatic accumulation of triglycerides. Bile acids have long been known to affect triglyceride homeostasis through a not completely understood mechanism. AIM: To analyse the effects of two different manipulations of bile acid circulation on non-alcoholic fatty liver disease. METHODS: Two animal models of non-alcoholic fatty liver disease were developed by either feeding rats with a choline deficient or with a high fat diet. After 4 weeks, rats were randomized to undergo either bile duct ligation, sham operation or cholic acid administration. RESULTS: During cholestasis there was an increased CYP7A1 expression, the rate limiting enzyme in bile acid synthesis, and a reduction of hepatic concentration of oxysterols, ligands of the liver X receptors. Target genes of the liver X receptors, involved in fatty acid and triglyceride synthesis, were down-regulated in association with decreased hepatic triglyceride content and improvement of fatty liver. Administration of cholic acid, ligand of farnesoid X receptor, also had a beneficial effect on fatty liver in rats on choline deficient diet. CONCLUSION: These results indicate that pharmacological approaches increasing the expression of CYP7A1 or stimulating farnesoid X receptor pathway could represent a promising treatment for non-alcoholic fatty liver disease.

Treatment of atherogenic liver based on the pathogenesis of nonalcoholic fatty liver disease: a novel approach to reduce cardiovascular risk?

Nonalcoholic fatty liver disease (NAFLD), which spans a spectrum of conditions ranging from simple steatosis to progressive nonalcoholic steatohepatitis (NASH), is the most common chronic liver disease and a relevant public health issue. The prevalence of NAFLD depends on adiposity, age, gender and ethnicity. The natural history of liver disease in those with NAFLD critically depends on liver histological changes. However, cardiovascular mortality is increased in NAFLD, particularly in middle-aged adults. Against such a background, this review consists of three sections. First, data on NAFLD as a novel mechanism of increased cardiovascular risk via hyperinsulinism, pro-thrombotic potential, and subclinical inflammation are summarized. Next, the role of atherogenic liver in the development of manifestations of oxidative stress and atherosclerosis is emphasized. Finally, whether and how treating NAFLD will mechanistically result in reduced cardiovascular risk through ameliorated metabolic syndrome is discussed.