C. Anzivino

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.

Age-related changes in bile acid synthesis and hepatic nuclear receptor expression.

Background  Recent data highlighted the role of nuclear receptors in the transcriptional regulation of the limiting enzyme of bile acid synthesis, cholesterol 7α‐hydroxylase, in cellular and animal models. This study was designed to analyze the effects of age on cholesterol 7α‐hydroxylase and related nuclear receptor expression in human livers.

Decreased hepatic expression of PPAR-gamma coactivator-1 in cholesterol cholelithiasis

Background  Cholesterol cholelithiasis (gallstone disease) is a common disease in the Western world. The aim of the present study was to analyze the hepatic expression of a number of nuclear receptors involved in bile acid metabolism in human cholesterol gallstone disease.

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.

Telomere and telomerase in chronic liver disease and hepatocarcinoma

The pathogenesis of liver cirrhosis is not completely elucidated. Although in the majority of patients, the risk factors may be identified in B and C viral hepatitis, alcohol intake, drugs or fatty liver disease, there is a small percentage of patients with no apparent risk factors. In addition, the evolution of chronic liver disease is highly heterogeneous from one patient to another. Among patient with identical risk factors, some rapidly progress to cirrhosis and hepatocellular carcinoma (HCC) whereas others have a benign course. Therefore, a genetic predisposition may contribute to the development of cirrhosis and HCC. Evidence supporting the role of genetic factors as a risk for cirrhosis has been accumulating during the past years. In addition to the results from epidemiological studies, polymorphisms studies and data on twins, the concept of telomere shortening as a genetic risk factor for chronic liver disease and HCC has been proposed. Here we review the literature on telomerase mutations, telomere shortening and liver disease including hepatocellular carcinoma.

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.

Increased appearance rate of 27-hydroxycholesterol in vivo in hypercholesterolemia: A possible compensatory mechanism

BACKGROUND AND AIMS The first step in the alternative pathway of bile acid biosynthesis is the 27-hydroxylation of cholesterol, which takes place both in liver and extrahepatic tissues. This pathway is believed to play a role in peripheral cholesterol degradation. Aim of this study was to investigate the impact of hyperlipidemia on 27-hydroxycholesterol appearance rate, and to assess the effects induced by treatment with statins. METHODS AND RESULTS Seven patients with familial hypercholesterolemia and eight patients with familial combined hyperlipidemia underwent determination of 27-hydroxylation rates in vivo by i.v. infusion of deuterated 27-hydroxycholesterol. Isotope enrichment was assayed by gas chromatography-mass spectrometry, allowing to calculate 27-hydroxycholesterol appearance rates. Six normocholesterolemic subjects were regarded as controls. In some hypercholesterolemic patients the infusions were repeated during treatment with atorvastatin or rosuvastatin. Hydroxylation rates were higher in hypercholesterolemic patients (8.7 ± 2.5 mg/h; controls, 3.4 ± 2.0 mg/h; combined hyperlipidemia, 4.4 ± 1.6 mg/h; mean ± SD, P < 0.01 vs both). After statin treatment, both plasma cholesterol levels and hydroxylation rates dropped by nearly 50%. No difference was detectable between the two statins. A linear correlation was shown between plasma cholesterol and 27-hydroxylation rates. CONCLUSION Hypercholesterolemia associates with increased 27-hydroxycholesterol appearance rates, which decrease during hypocholesterolemic treatment. The correlation with cholesterol levels supports the view that 27-hydroxylation may act as a compensatory mechanism in a condition of larger plasma cholesterol pool. A regulatory role for hepatic and extrahepatic nuclear receptors seems reasonable. These data prompt novel pharmacological approaches for the management of hypercholesterolemia and the prevention of atherosclerosis.

Correlation between plasma levels of 7alpha-hydroxy-4-cholesten-3-one and cholesterol 7alpha-hydroxylation rates in vivo in hyperlipidemic patients.

BACKGROUND/AIM Hepatic bile acid synthesis is the main mechanism whereby the organism can degrade cholesterol. Plasma levels of 7alpha-hydroxy-4-cholesten-3-one have been reported to reflect bile acid synthesis and the expression or activity of the limiting enzyme of the main biosynthetic pathway, cholesterol 7alpha-hydroxylase. Aim of this study was to correlate the levels of this metabolite with the rates of cholesterol 7alpha-hydroxylation in vivo, a direct measurement of bile acid synthesis, in hyperlipidemic patients. DESIGN Concentrations of 7alpha-hydroxy-4-cholesten-3-one were assayed by gas-liquid chromatography: mass spectrometry in plasma samples obtained in 18 patients with primary hyperlipoproteinemia who previously underwent determination of cholesterol 7alpha-hydroxylation rates in vivo by tritium release analysis. Both determinations were performed in basal conditions and after treatment with hypolipidemic drugs (the fibric acid derivatives gemfibrozil and bezafibrate, cholestyramine alone or associated with simvastatin). RESULTS Changes in plasma 7alpha-hydroxy-4-cholesten-3-one profile closely reflected in vivo cholesterol 7alpha-hydroxylation rates during treatment with fibrates, cholestyramine and cholestyramine plus simvastatin. When plotting determinations from all studies (n=40), a very strict correlation was disclosed between plasma 7alpha-hydroxy-4-cholesten-3-one and cholesterol 7alpha-hydroxylation rates (r=0.81, P<0.001). CONCLUSIONS Plasma 7alpha-hydroxy-4-cholesten-3-one closely mirrors measurements of cholesterol 7alpha-hydroxylation rates in vivo in hyperlipidemic subjects and therefore stands as a reliable marker of global bile acid synthesis. In view of the correlation observed, these data may help to interpret changes of plasma levels of this metabolite in terms of cholesterol balance quantification.

Review article: hyperlipidaemia and cardiovascular risk

Hyperlipidaemia represents a determinant for the development of atherosclerosis and an important risk factor for cardiovascular disease, particularly in the context of the insulin resistance syndrome. This is characterized by alterations in the profile of plasma lipoprotein including high triglyceride levels, low high‐density lipoprotein cholesterol concentrations and the appearance of qualitatively modified, small‐dense low‐density lipoproteins. Many charts and algorithms have been developed to estimate the entity of coronary and cardiovascular risk as related to dyslipidaemia, on the basis of additional individual risk factors and conditions: most include age and gender, smoking status, hypertension and diabetes. They should preferably be utilized in consistent patient populations, in terms of geographical areas and general risk profile. Pharmacological treatment of dyslipidaemia, in particular with statin drugs, was shown to greatly improve cardiovascular morbidity and mortality. A body of evidence also underlines the need for a multidisciplinary approach, integrating non‐pharmacological lifestyle and diet interventions, as well as treatment of concomitant diseases (hypertension and diabetes).

17β-estradiol prevents cytotoxicity from hydrophobic bile acids in HepG2 and WRL-68 cell cultures

Background:  Epidemiological and clinical studies suggest the possibility that estrogens might have a cytoprotective effect on the liver. The aim of the present study was to test the hypothesis that 17β‐estradiol (E2) prevents hepatocellular damage induced by deoxycholic acid (DCA), a hydrophobic bile acid.