Dietary patterns in the French adult population: a study from the second French national cross-sectional dietary survey (INCA2) (2006-2007).

Identification and characterisation of dietary patterns are needed to define public health policies to promote better food behaviours. The aim of this study was to identify the major dietary patterns in the French adult population and to determine their main demographic, socio-economic, nutritional and environmental characteristics. Dietary patterns were defined from food consumption data collected in the second French national cross-sectional dietary survey (2006-2007). Non-negative-matrix factorisation method, followed by a cluster analysis, was implemented to derive the dietary patterns. Logistic regressions were then used to determine their main demographic and socio-economic characteristics. Finally, nutritional profiles and contaminant exposure levels of dietary patterns were compared using ANOVA. Seven dietary patterns, with specific food consumption behaviours, were identified: 'Small eater', 'Health conscious', 'Mediterranean', 'Sweet and processed', 'Traditional', 'Snacker' and 'Basic consumer'. For instance, the Health-conscious pattern was characterised by a high consumption of low-fat and light products. Individuals belonging to this pattern were likely to be older and to have a better nutritional profile than the overall population, but were more exposed to many contaminants. Conversely, individuals of Snacker pattern were likely to be younger, consumed more highly processed foods, had a nutrient-poor profile but were exposed to a limited number of food contaminants. The study identified main dietary patterns in the French adult population with distinct food behaviours and specific demographic, socio-economic, nutritional and environmental features. Paradoxically, for better dietary patterns, potential health risks cannot be ruled out. Therefore, this study demonstrated the need to conduct a risk-benefit analysis to define efficient public health policies regarding diet.

Dietary patterns of French adults: associations with demographic, socio-economic and behavioural factors.

BACKGROUND: Although the French eating model may differ from those of other countries, no studies to date have investigated dietary patterns in a wide age range of adults and at the national level. We aimed to identify dietary patterns (DP) of French adults and assess their associations with demographic, socio-economic and behavioural factors. METHODS: The present study included 2624 adults (1087 men, 1537 women) aged 18-79 years from the cross-sectional national French INCA2 dietary survey. Dietary data were collected using a 7-day estimated food record. Clusters of DP were derived using principal component analysis and clustering, conjointly. Age-adjusted logistic regression analyses were used to investigate the association between DP and correlates. RESULTS: Five DP were identified, namely 'traditional', 'prudent', 'diversified', 'processed' and 'sandwiches'. Men were more likely to follow a traditional diet and women the 'prudent' pattern. Members of the 'processed' and 'sandwiches' patterns were younger compared to non-members. Healthier dietary patterns were overall positively associated with a higher socio-economic position, healthier behaviours (in terms of sedentary behaviours and smoking status) and lower body mass index. Under-reporting of energy intake, restrictive diet to lose weight and dietary supplement consumption were also related to specific DP, although differentially in men and women. Associations with contextual factors (i.e. household composition, agglomeration size and region) were also observed. CONCLUSIONS: The identification of adults' dietary patterns and associated behaviours (all modifiable) is important for the conceptualisation of multi-behavioural programs. The additional information on social and environmental correlates is also essential for targeting the most vulnerable population groups in the context of such public health interventions.

RIPK1 promotes death receptor-independent caspase-8-mediated apoptosis under unresolved ER stress conditions.

Accumulation of unfolded proteins in the endoplasmic reticulum (ER) causes ER stress and results in the activation of the unfolded protein response (UPR), which aims at restoring ER homeostasis. However, when the stress is too severe the UPR switches from being a pro-survival response to a pro-death one, and the molecular mechanisms underlying ER stress-mediated death have remained incompletely understood. In this study, we identified receptor interacting protein kinase 1 (RIPK1)-a kinase at the crossroad between life and death downstream of various receptors-as a new regulator of ER stress-induced death. We found that Ripk1-deficient MEFs are protected from apoptosis induced by ER stressors, which is reflected by reduced caspase activation and PARP processing. Interestingly, the pro-apoptotic role of Ripk1 is independent of its kinase activity, is not regulated by its cIAP1/2-mediated ubiquitylation, and does not rely on the direct regulation of JNK or CHOP, two reportedly main players in ER stress-induced death. Instead, we found that ER stress-induced apoptosis in these cells relies on death receptor-independent activation of caspase-8, and identified Ripk1 upstream of caspase-8. However, in contrast to RIPK1-dependent apoptosis downstream of TNFR1, we did not find Ripk1 associated with caspase-8 in a death-inducing complex upon unresolved ER stress. Our data rather suggest that RIPK1 indirectly regulates caspase-8 activation, in part via interaction with the ER stress sensor inositol-requiring protein 1 (IRE1).

RIPK3 contributes to TNFR1-mediated RIPK1 kinase-dependent apoptosis in conditions of cIAP1/2 depletion or TAK1 kinase inhibition.

Receptor-interacting protein kinase (RIPK) 1 and RIPK3 have emerged as essential kinases mediating a regulated form of necrosis, known as necroptosis, that can be induced by tumor necrosis factor (TNF) signaling. As a consequence, inhibiting RIPK1 kinase activity and repressing RIPK3 expression levels have become commonly used approaches to estimate the contribution of necroptosis to specific phenotypes. Here, we report that RIPK1 kinase activity and RIPK3 also contribute to TNF-induced apoptosis in conditions of cellular inhibitor of apoptosis 1 and 2 (cIAP1/2) depletion or TGF-ß-activated kinase 1 (TAK1) kinase inhibition, implying that inhibition of RIPK1 kinase activity or depletion of RIPK3 under cell death conditions is not always a prerequisite to conclude on the involvement of necroptosis. Moreover, we found that, contrary to cIAP1/2 depletion, TAK1 kinase inhibition induces assembly of the cytosolic RIPK1/Fas-associated protein with death domain/caspase-8 apoptotic TNF receptor 1 (TNFR1) complex IIb without affecting the RIPK1 ubiquitylation status at the level of TNFR1 complex I. These results indicate that the recruitment of TAK1 to the ubiquitin (Ub) chains, and not the Ub chains per se, regulates the contribution of RIPK1 to the apoptotic death trigger. In line with this, we found that cylindromatosis repression only provided protection to TNF-mediated RIPK1-dependent apoptosis in condition of reduced RIPK1 ubiquitylation obtained by cIAP1/2 depletion but not upon TAK1 kinase inhibition, again arguing for a role of TAK1 in preventing RIPK1-dependent apoptosis downstream of RIPK1 ubiquitylation. Importantly, we found that this function of TAK1 was independent of its known role in canonical nuclear factor-κB (NF-κB) activation. Our study therefore reports a new function of TAK1 in regulating an early NF-κB-independent cell death checkpoint in the TNFR1 apoptotic pathway. In both TNF-induced RIPK1 kinase-dependent apoptotic models, we found that RIPK3 contributes to full caspase-8 activation independently of its kinase activity or intact RHIM domain. In contrast, RIPK3 participates in caspase-8 activation by acting downstream of the cytosolic death complex assembly, possibly via reactive oxygen species generation.

Associations between usual school lunch attendance and eating habits and sedentary behaviour in French children and adolescents.

BACKGROUND/OBJECTIVE: Our objective was to investigate whether school lunch attendance was associated with overall eating habits and sedentary behaviour in a French sample of children and adolescents. SUBJECTS/METHODS: Data for the study were taken from the second French cross-sectional dietary survey (INCA2-2006-07). In total, 1413 school children aged 3-17 years old were classified according to their school type and their usual school lunch attendance. Eating habits included meal regularity, dietary diversity, purchase in vending machine, snacking habits and frequency of eating in fast-foods. Two composite indices of eating habits were derived from multiple correspondence analyses. Sedentary behaviour was assessed by the average daily screen times for TV and computer. The association between school lunch attendance and each variable was tested. Multivariate association between school lunch attendance and the composite indices of eating habits and sedentary behaviours was studied. RESULTS: In all, 69.0% (CI(95%): 64.2-73.9) of secondary school children and 63.0% (CI(95%): 58.5-67.5) of pre- and elementary school children usually attended school lunch at least once a week. Pre- and elementary school children attending school lunches showed a higher dietary diversity score (P=0.02) and ate morning snacks more frequently (P=0.02). In secondary school children, attending school canteen was related to a lower rate of skipping breakfast (P=0.04) and main meals (P=0.01). In all school children, school lunch attendance was simultaneously associated with healthier overall eating habits and less sedentary behaviour. CONCLUSION: In France, children attending school canteens seem to have healthier eating habits and display less sedentary behaviour, independently of their socio-economic and demographic background.

Accounting for the multidimensional nature of the relationship between adult obesity and socio-economic status: the French second National Individual Survey on Food Consumption (INCA 2) dietary survey (2006-07).

The objective was to study the multidimensional nature of the relationship between adult obesity (OB) and socio-economic status (SES), using comprehensive indices of SES taken separately or synthesised in an overall index. A nationally representative sample of adults aged 18-79 years was taken from the French second National Individual Survey on Food Consumption (INCA 2) dietary survey (2006-07). Weight and height were measured and OB defined as BMI ≥ 30 kg/m2. SES variables were reported in questionnaires and included occupation, education and characteristics of household wealth. Composite indices of SES (household wealth and overall SES indices) were computed by correspondence analysis, and relationships with OB were investigated with logistic regression analysis. In total, 11·8 (95 % CI 10·1, 13·4) % of French adults were obese, without significant difference by sex. While no significant relationship was observed in men, all SES indicators were inversely correlated to OB in women. Both education and the household wealth index were retained in the stepwise multivariate model, confirming that different socio-economic variables are not necessarily proxies of each other regarding the OB issue. On the other hand, 'controlling for SES' while including several measures of SES in multivariate models may lead to collinearity, and thus over-adjustment. A more integrative approach may be to derive a synthetic index by including the SES factors available in a given study. Beyond this methodological perspective, understanding how OB is related to the different dimensions of SES should help to target the more vulnerable groups and increase the effectiveness of prevention.

[Schools meals in French secondary state schools: compliance to national recommendations and schools catering patterns]. / La restauration scolaire dans les établissements publics français du second degré : respect des recommandations nationales et profils d'établissements.

BACKGROUND: Recent reports on the lack of nutritional quality of meals served in schools have led public authorities to draft, in 1999, recommendations for restoring a balanced food supply. Following the survey carried out by the French food safety Agency in 2005-2006, which highlighted gaps in the implementation of these recommendations, a law passed in July 2010 plans to make these recommendations mandatory, as their 2007 revised version. Thus, the objective of this study was to assess initial school compliance with regard to this last revised version of the recommendations and to identify school patterns through their catering management and implication in a dietary project. METHODS: Seven hundred and seven secondary state schools were questioned (570 were administrated by the Ministry of Education and 137 by the Ministry of Agriculture) on their catering practices. Twenty consecutive menus from each school were also analyzed with a specific coding system to establish its nutritional composition for comparison with the 2007 recommendations. RESULTS: On average, schools complied with half of the recommendations. Good compliance was observed with the 2007 recommendations concerning fried products, starchy foods, fruits, and dairy products whereas very few schools were in compliance with recommendations concerning fish, cheeses and sweetened desserts containing less than 15 % fat and more than 20 g of sugar per portion. Furthermore, compliance with recommendations was significantly better for lunch meals, and even better for agricultural establishments. A 5-component meal was also associated with greater compliance with the recommendations. In addition, four school patterns were identified based on catering management practices. The first two categories of establishments had knowledge of the recommendations but exhibited different levels of application. The last two types of establishments had no knowledge of the recommendations and differed in their catering management practices. CONCLUSION: Compliance with recommendations was contrasted, with high adequacy for some guidelines and low for others. Nevertheless, application of the current guidelines and real implication of the school in a dietary project did improve the dietary offer in such schools.

Core food of the French food supply: second Total Diet Study.

As first described in the 1980s, the core food intake model allows a precise assessment of dietary nutrient intake and dietary exposure to contaminants insofar as it reflects the eating habits of a target population and covers the most important foods in terms of consumption, selected nutrient and contaminant contribution. This model has been used to set up the sampling strategy of the second French Total Diet Study (TDS) with the aim of obtaining a realistic panorama of nutrient intakes and contaminant exposure for the whole population, useful for quantitative risk assessment. Data on consumption trends and eating habits from the second French individual food consumption survey (INCA2) as well as data from a 2004 purchase panel of French households (SECODIP) were used to identify the core foods to be sampled. A total of 116 core foods on a national scale and 70 core foods on a regional scale were selected according to (1) the consumption data for adults and children, (2) their consumer rates, and (3) their high contribution to exposure to one or more contaminants of interest. Foods were collected in eight French regions (36 cities) and prepared 'as consumed' to be analysed for their nutritional composition and contamination levels. A total of 20 280 different food products were purchased to make up the 1352 composite samples of core foods to be analysed for additives, environmental contaminants, pesticide residues, trace elements and minerals, mycotoxins and acrylamide. The establishment of such a sampling plan is essential for effective, high-quality monitoring of dietary exposure from a public health point of view.

Trends in child overweight rates and energy intake in France from 1999 to 2007: relationships with socioeconomic status.

Our objectives were (i) to assess the current prevalence of childhood overweight (including obesity) (OWOB) in France and its relationship with comprehensive socioeconomic status (SES) indicators and (ii) to examine trends in OWOB prevalence and changes in energy intake (EI) and sedentary behavior (SED) based on the previous INCA 1 (Individuelle Nationale des Consommations Alimentaires) data (1998-1999). A representative sample of children aged 3-14 (n = 1,030) was taken from the 2006-2007 cross-sectional INCA 2 food consumption survey. Weight and height were measured. The prevalence of OWOB was estimated according to the IOTF (International Obesity Task Force) definition. Average daily EI was evaluated using a 7-day food record. SED (screen time) and SES were reported by answering questionnaires. SES indicators included the occupation and level of education of the head of the household (HH), and variables describing household wealth. Composite indices of SES were computed by correspondence analysis, and relationships with OWOB were explored by logistic regression analysis. In total, 14.5% (95% CI: 12.1-17.0) of the children were OWOB. All SES indicators were inversely correlated to OWOB. Average EI was equal to 1,739 kcal/day. Daily, children spent 113.5 min watching television, and 38.5 min playing video games or using a computer. Compared to the INCA 1 study, OWOB prevalence was not significantly different, EI was lower, and SED was higher. These trends were the same across all occupational categories of heads of household. Although overall rates of childhood OWOB are currently stabilizing, no change was observed in the strong inverse socioeconomic gradient of OWOB between the two studies.

[Comparison of two national food surveys (INCA 1 1998-99 and Health Nutrition Barometer 2002) with regard to five food recommendations of the National Nutrition and Health Program]. / Comparaison de deux enquêtes nationales de consommations alimentaires (INCA 1 1998/99 et Baromètre santé nutrition 2002) au regard de cinq objectifs alimentaires du Programme national nutrition santé.

BACKGROUND: Monitoring the dietary intake of the French population requires the implementation and regular renewal of representative national survey. As these surveys can use different methodologies (food frequency questionnaire, 24 hour recall, 3 or 7-day dietary record...), it seems useful to check whether they supply similar results. The aim of this study is to determine whether two representative national surveys with different methodologies can be used alternately to monitor changes in food consumption of the French population. METHOD: Percentages of consumers aged 15-75 were compared between two national food surveys (Health Nutrition Barometer 2002 and INCA 1 1998-99) with respect to five food frequency recommendations of the French National Nutrition and Health Program. RESULTS: The same public health priorities were found in both surveys: the food groups were graded according to the same hierarchy of adequate food intake prevalences (ascending: fruits and vegetables, dairy products, fish, starchy foods and meat-fish-egg products). On the other hand, significant statistical different elements were pointed out in a few food groups which may be explained by methodological patterns. Definitions of portions and food groups, survey duration and seasons are indeed important parameters to be considered when comparing surveys. CONCLUSION: The results show the need to elaborate standardized methods for comparison of food consumption surveys, which can be useful for the evaluation of the national nutritional recommendations. The methodological limitations described in this study also indicate that the quantitative description of food intake trends should improve when established by the results of the same regularly repeated survey.

Orthotopic liver transplantation for mitochondrial respiratory chain disorders: a study of 5 children.

BACKGROUND: Liver involvement in mitochondrial respiratory chain disorders (MRCD) frequently ends in liver failure and death. Because of the high risk of extrahepatic, particularly neuromuscular, manifestations of the disease, the indication of orthotopic liver transplantation (OLT) in these patients remains controversial. We report on 5 such children in whom OLT was carried out, in an attempt to help clarify the matter. PATIENTS: Patients 1 and 2 presented with fulminant liver failure at ages 7 and 6 months respectively. Emergency liver transplantation was performed before etiological investigations were completed. Retrospective examination of the explanted livers showed defects in complexes I, III and IV. In patient 1, severe neurological deterioration occurred 2 months after OLT with fatal outcome 9 months later. Patient 2 is alive 22 months after OLT with moderate motor impairment. Patients 3, 4 and 5 presented with progressive liver failure before 6 months of age. Surgical liver biopsies displayed a 50% defect in complex IV (patient 3), a defect in complexes I, IV (patient 4) and in complexes I, III, IV (patient 5). Because there was no clinical extrahepatic involvement on investigations, OLT was carried out in these patients. Patient 3 died of multiple organ failure soon after OLT, patients 4 and 5 are alive respectively 21 months and 12 months after OLT with normal neurological examination. CONCLUSION: OLT may be a valid therapeutic option in infants with delayed liver cell failure due to MRCD, only after performing in emergency a thorough inves tigation to exclude clinically significant extrahepatic, especially neuromuscular, involvement.

Bulk analysis by IR laser ablation inductively coupled plasma atomic emission spectrometry.

Two laser ablation systems dedicated to bulk analysis were evaluated for steel and PVC samples, using inductively coupled plasma atomic emission spectrometry detection. These systems were characterized by the use of a Nd:YAG laser operating at 1064 nm, the absence of observation device and a large laser spot size. The 1064 nm wavelength was selected to avoid the use of frequency-multiplying optics, and to be less critical to the sampling position. Calibration graphs and limits of detection are given for both types of materials. LODs were in the range 3-120 microg/g for steel, and in the range 0.07-15 microg/g for PVC. In the case of steel samples, similar calibration graph slopes were obtained between polished and unpolished samples.

Paediatric liver transplantation with a split graft: experience at Bicêtre.

UNLABELLED: This study evaluates the results of paediatric liver transplantation (PLT) with split liver grafts at Bicêtre hospital. PATIENTS AND METHODS: Between January 1, 1988 and December 31, 1995, 205 PLT were performed in 180 children. One auxiliary PLT was excluded from the study. The graft was a whole (WLG), reduced (RLG) and split liver graft (SLG) in 76, 112 and 16 cases respectively. The SLG consisted of segments II + III in 14 cases, and II + III + IV in 2 cases. Results of PLT with SLT, RLT and WLG were retrospectively compared. Minimal follow-up was 12 months. RESULTS: In elective PLT, actual 1 year patient (graft) survival were 93.3% (84.4%) with WLG (n = 64), 84.1% (76.4%) with RLG (n = 72), 81.8% (81.8%) with SLG (n = 11). In urgent LT, actual patient (graft) survival were 100% (83.3%) with WLG (n = 6), 58.6% (52.5%) with RLG (n = 40), 25% (20%) with SLG (n = 5). Specific complications of the splitting technique were: 2 Budd-Chiari syndromes in 2 early patients, without any new case after modification of the technique of left hepatic vein to inferior vena cava anastomosis; 4 bile leaks (25%) from the left hepatic duct to Roux-en-Y loop anastomosis. DISCUSSION: In our experience, the results of PLT with SLG were satisfactory in the elective situation, but disappointing in urgent cases. In the current context of liver graft shortage, appropriate use of this sophisticated and demanding technique depends on the experience of the team, recipient's condition, and logistic considerations.

[Smooth muscle mesentery associated with Epstein-Barr virus (EBV). Report of a case in a child with a liver transplant under FK506 regimen]. / Tumeur musculaire lisse mésentérique associée au virus d'Epstein-Barr (EBV). A propos d'un cas chez un enfant transplanté hépatique sous FK 506.

Smooth-muscle tumors, benign and malignant, are increasingly recognized in children who are immunocompromised because of HIV infection and organ transplantation. We report a case of an EBV-associated smooth-muscle tumor, of unusual location arising in a seven-year-old post-transplant patient who was previously treated for a lymphoproliferative disease. Five years after liver transplantation, a mesenteric tumor was diagnosed. The tumor was composed of spindle cells with smooth-muscle features. Immunohistochemical analysis was positive for muscle-specific actin and desmin, negative for EBV latent membrane protein (LMP-1). In situ hybridization revealed nuclear EBV sequences. This case underlines the role of EBV infection in the development of unusual smooth-muscle tumors after organ transplantation. The evolution of these rare tumors is uncertain.

Protein C, protein S and antithrombin III in children with portal vein obstruction.

BACKGROUND/AIMS: Portal vein obstruction is the most common single cause of portal hypertension in children and its cause is unknown in most instances. The aim of the present study was to evaluate the incidence of protein C, protein S and antithrombin III deficiencies and to screen for possible genetic deficiencies of these proteins. METHODS: A prospective study was undertaken in 20 consecutive children with portal vein obstruction, their parents and 20 matched healthy children. RESULTS: Children with portal vein obstruction displayed a reduction in protein C (p<0.05), protein S (p<0.0001), and antithrombin III (p<0.001) activities as compared with controls. Protein C and protein S activities were below 60% in nine and eleven of the children with portal vein obstruction, respectively, and antithrombin III activities were below or equal to 85% in ten of them. Repeated assay of protein C activity in seven children following a surgical portosystemic shunt showed a decrease as compared with preoperative values. Protein C, protein S and antithrombin III were normal in all parents, except two mothers in whom the levels of protein S activity and protein S antigen were found to be either below or at the lower limit of the normal range. CONCLUSIONS: These results indicate that protein C, protein S and/or antithrombin III deficiencies are frequently found in children with portal vein obstruction but are not likely to be of genetic origin in most cases.

Neonatal and delayed-onset liver involvement in disorders of oxidative phosphorylation.

Inborn errors of oxidative phosphorylation have been recognized as possible causes of hepatic failure in the neonate, and respiratory enzyme deficiencies have been described in the liver of affected individuals. On the basis of a series of 22 cases, we describe respiratory enzyme deficiency as a cause of early-onset fatal hepatic failure with frequent neurologic involvement. In addition, we have identified a delayed-onset form of hepatic failure with a milder clinical course and inconstant neurologic involvement. Thus we suggest that genetic defects of oxidative phosphorylation be considered as a cause of liver dysfunction in infancy, regardless of the severity of the disease.

Ontogenic expression of the Na(+)-independent organic anion transporting polypeptide (oatp) in rat liver and kidney.

BACKGROUND/AIMS: A cDNA (2.7 kb) encoding a rat liver basolateral Na(+)-independent organic anion transporter (oatp) has recently been cloned. The aim of the present study was to clarify the mechanisms of bile formation during development. METHODS: The ontogenic expression of oatp was examined by northern blot analysis and in situ hybridization in rat liver. The expression of oatp in the kidney was also studied in parallel. RESULTS: In the liver, a 2.5 kb oatp mRNA was first detected in the fetus on day 16 of gestation. The amount of this oatp mRNA remained stable during the perinatal period and increased dramatically after weaning. Other transcripts probably corresponding to oatp-related mRNAs also display a late expression pattern in the perinatal period. In contrast, Na+/taurocholate transporting polypeptide (Ntcp) mRNA was first detected on day 20 of gestation. By in situ hybridization, oatp mRNA was localized into hepatocytes and distributed without lobular heterogeneity. In the kidney, a single 2.4 kb oatp transcript was detected from birth to adult age. This transcript was exclusively distributed in the epithelial cells of the proximal tubules localized in the kidney cortex and the outer medulla. CONCLUSIONS: These results indicate that oatp undergoes a time-related expression in rat liver and kidney during development and that its gene transcription precedes Ntcp gene transcription in the liver. The delayed expression of oatp at the perinatal period may explain in part the immaturity of bile formation and the physiological neonatal cholestasis.

Defect of multidrug-resistance 3 gene expression in a subtype of progressive familial intrahepatic cholestasis.

Disruption of the murine mdr2 (multidrug-resistance) gene, which encodes a phosphatidylcholine flippase, leads to a hepatic disorder because of loss of biliary phospholipid secretion. Among the hereditary human cholestasis, a subtype of progressive familial intrahepatic cholestasis with high gamma-glutamyltranspeptidase (GGT) serum activity shares histological, biochemical, and genetic features with mice lacking mdr2 gene expression (mdr2 -/- mice). No MDR3 (human mdr2 homolog) messenger RNA (mRNA) was detected by Northern blotting in the liver of a patient suffering from this form of PFIC, and the biliary phospholipid level in a second patient was substantially decreased. Thus, the absence of the MDR3 P-glycoprotein may be responsible for this type of PFIC, which, as in the murine model, may be due to a toxic effect of bile acids on the biliary epithelium in absence of biliary phospholipids.