The Liver under the Spotlight: Bile Acids and Oxysterols as Pivotal Actors Controlling Metabolism

Among the myriad of molecules produced by the liver, both bile acids and their precursors, the oxysterols are becoming pivotal bioactive lipids which have been underestimated for a long time. Their actions are ranging from regulation of energy homeostasis (i.e., glucose and lipid metabolism) to inflammation and immunity, thereby opening the avenue to new treatments to tackle metabolic disorders associated with obesity (e.g., type 2 diabetes and hepatic steatosis) and inflammatory diseases. Here, we review the biosynthesis of these endocrine factors including their interconnection with the gut microbiota and their impact on host homeostasis as well as their attractive potential for the development of therapeutic strategies for metabolic disorders.

Intestinal NAPE-PLD contributes to short-term regulation of food intake via gut-to-brain axis

Our objective was to explore the physiological role of the intestinal endocannabinoids in the regulation of appetite upon short-term exposure to high-fat-diet (HFD) and understand the mechanisms responsible for aberrant gut-brain signaling leading to hyperphagia in mice lacking Napepld in the intestinal epithelial cells (IECs). We generated a murine model harboring an inducible NAPE-PLD deletion in IECs (Napepld^ΔIEC). After an overnight fast, we exposed wild-type (WT) and Napepld^ΔIEC mice to different forms of lipid challenge (HFD or gavage), and we compared the modification occurring in the hypothalamus, in the vagus nerve, and at endocrine level 30 and 60 min after the stimulation. Napepld^ΔIEC mice displayed lower hypothalamic levels of N-oleoylethanolamine (OEA) in response to HFD. Lower mRNA expression of anorexigenic Pomc occurred in the hypothalamus of Napepld^ΔIEC mice after lipid challenge. This early hypothalamic alteration was not the consequence of impaired vagal signaling in Napepld^ΔIEC mice. Following lipid administration, WT and Napepld^ΔIEC mice had similar portal levels of glucagon-like peptide-1 (GLP-1) and similar rates of GLP-1 inactivation. Administration of exendin-4, a full agonist of GLP-1 receptor (GLP-1R), prevented the hyperphagia of Napepld^ΔIEC mice upon HFD. We conclude that in response to lipid, Napepld^ΔIEC mice displayed reduced OEA in brain and intestine, suggesting an impairment of the gut-brain axis in this model. We speculated that decreased levels of OEA likely contributes to reduce GLP-1R activation, explaining the observed hyperphagia in this model. Altogether, we elucidated novel physiological mechanisms regarding the gut-brain axis by which intestinal NAPE-PLD regulates appetite rapidly after lipid exposure.

Hepatic NAPE-PLD Is a Key Regulator of Liver Lipid Metabolism

Diverse metabolic disorders have been associated with an alteration of N-acylethanolamine (NAE) levels. These bioactive lipids are synthesized mainly by N-acylphosphatidylethanolamine-selective phospholipase D (NAPE-PLD) and influence host metabolism. We have previously discovered that NAPE-PLD in the intestine and adipose tissue is connected to the pathophysiology of obesity. However, the physiological function of NAPE-PLD in the liver remains to be deciphered. To study the role of liver NAPE-PLD on metabolism, we generated a new mouse model of inducible Napepld hepatocyte-specific deletion (Napepld∆Hep mice). In this study, we report that Napepld∆Hep mice develop a high-fat diet-like phenotype, characterized by an increased fat mass gain, hepatic steatosis and we show that Napepld∆Hep mice are more sensitive to liver inflammation. We also demonstrate that the role of liver NAPE-PLD goes beyond the mere synthesis of NAEs, since the deletion of NAPE-PLD is associated with a marked modification of various bioactive lipids involved in host homeostasis such as oxysterols and bile acids. Collectively these data suggest that NAPE-PLD in hepatocytes is a key regulator of liver bioactive lipid synthesis and a dysregulation of this enzyme leads to metabolic complications. Therefore, deepening our understanding of the regulation of NAPE-PLD could be crucial to tackle obesity and related comorbidities.

Hepatic MyD88 regulates liver inflammation by altering synthesis of oxysterols

This study aimed to investigate the function of hepatic myeloid differentiation primary response gene 88 (MyD88), a central adaptor of innate immunity, in metabolism. Although its role in inflammation is well known, we have recently discovered that MyD88 can also mediate energy, lipid, and glucose metabolism. More precisely, we have reported that mice harboring hepatocyte-specific deletion of MyD88 (Myd88^ΔHep) were predisposed to glucose intolerance, liver fat accumulation, and inflammation. However, the molecular events explaining the onset of hepatic disorders and inflammation remain to be elucidated. To investigate the molecular mechanism, Myd88^ΔHep and wild-type (WT) mice were challenged by two complementary approaches affecting liver lipid metabolism and immunity. The first approach consisted of a short-term exposure to high-fat diet (HFD), whereas the second was an acute LPS injection. We discovered that upon 3 days of HFD Myd88^ΔHep mice displayed an increase in liver weight and liver lipids compared with WT mice. Moreover, we found that bile acid and oxysterol metabolism were deeply affected by the absence of hepatic MyD88. Our data suggest that the negative feedback loop suppressing bile acid synthesis was impaired (i.e., ERK activity was decreased) in Myd88^ΔHep mice. Finally, the predisposition to inflammation sensitivity displayed by Myd88^ΔHep mice may be caused by the accumulation of 25-hydroxycholesterol, an oxysterol linked to inflammatory response and metabolic disorders. This study highlights the importance of MyD88 on both liver fat accumulation and cholesterol-derived bioactive lipid synthesis. These are two key features associated with metabolic syndrome. Therefore, investigating the regulation of hepatic MyD88 could lead to discovery of new therapeutic targets.

Microbial regulation of organismal energy homeostasis

The gut microbiome has emerged as a key regulator of host metabolism. Here we review the various mechanisms through which the gut microbiome influences the energy metabolism of its host, highlighting the complex interactions between gut microbes, their metabolites and host cells. Among the most important bacterial metabolites are short-chain fatty acids, which serve as a direct energy source for host cells, stimulate the production of gut hormones and act in the brain to regulate food intake. Other microbial metabolites affect systemic energy expenditure by influencing thermogenesis and adipose tissue browning. Both direct and indirect mechanisms of action are known for specific metabolites, such as bile acids, branched chain amino acids, indole propionic acid and endocannabinoids. We also discuss the roles of specific bacteria in the production of specific metabolites and explore how external factors, such as antibiotics and exercise, affect the microbiome and thereby energy homeostasis. Collectively, we present a large body of evidence supporting the concept that gut microbiota-based therapies can be used to modulate host metabolism, and we expect to see such approaches moving from bench to bedside in the near future.

Characterization of fiber ultrashort pulse delivery for nonlinear endomicroscopy

In this work, we present a detailed characterization of a small-core double-clad photonic crystal fiber, dedicated and approved for in vivo nonlinear imaging endomicroscopy. A numerical and experimental study has been performed to characterize the excitation and collection efficiencies through a 5 m-long optical fiber, including the pulse duration and spectral shape. This was first done without any distal optics, and then the performances of the system were studied by using two kinds of GRIN lenses at the fiber output. These results are compared to published data using commercial double clad fibers and GRIN lenses.

Physico-chemical characteristics of topsoil for contrasted forest, agricultural, urban and industrial land uses in France

Soil quality is related to soil characteristics such as fertility and contamination. The aim of this study is to assess the effect of land use on these soil characteristics and to confirm the following anthropisation gradient: (i) forest, (ii) grassland, (iii) cultivated, (iv) orchard and vineyard, (v) urban vegetable garden, and (vi) SUITMA (urban, industrial, traffic, mining and military areas). A database comprising the characteristics of 2451 soils has been constituted. In order to compare the topsoils from six contrasting land uses, a principal components analysis (PCA) was performed on nine geochemical variables (C, N, pH, POlsen, total Cd, Cu, Ni, Pb, Zn). The first axis of the PCA is interpreted as a global increase of topsoil metallic elements along the anthropisation gradient. Axis 2 reflects the variability of fertility levels. Human activity increases the pressure on soils along the proposed gradient according to six different distribution patterns. This better knowledge of topsoil quality and its dependence on current land use should therefore help to manage and preserve the soil mantle.

Optimization and characterization of nonlinear excitation and collection through a gradient-index lens for high-resolution nonlinear endomicroscopy

We report a study of gradient index (GRIN) lenses as a miniaturized micro-objective for in vivo imaging in the context of the development of a nonlinear endomicroscope. A numerical study of the parameters influencing the lateral resolution, excitation, and collection efficiency, when GRIN lens is coupled with a double clad fiber (DCF), is exposed. Four commercial DCFs, previously identified from the literature as potential endoscopic fibers, are simulated. Then, an experimental study characterizes two GRIN lenses (one commercial, one homemade) by their dispersion and nonlinear effects, potential intrinsic fluorescence, and use for fluorescence lifetime measurements. Images of neural cells from brain tissues of mice through a GRIN lens are presented.

[How to write, how to implement and how to evaluate a practice guideline in order to improve quality of care?]

Initiatives of clinical practices improvement have been gradually developing in France for 20 years. Nevertheless, effective implementation of change is still difficult for numerous reasons. The use of clinical practices guidelines is one of the different ways of improvement. It is however necessary to adapt these national guidelines to the specificities of the hospital and the team, to ensure implementation and appropriation by the professionals. These recommendations are thus translated into applicable and concrete standard operating procedures. These documents have to be built by and for the concerned professionals. They are also communication and training tools, precise, directive, uniform in terms of presentation and attractive visually. Once drafted, they have to be distributed widely to the professionals to facilitate implementation. The simple distribution of the recommendations is insufficient to modify the clinical practices and require association of several methods of promotion for an optimal appropriation. How then to make sure of their effective use? Practices evaluation is one of the steps of continuous professional development, including continuous training and analysis of clinical practices by using methods promoted by the "Haute Autorité de santé". One of them is the clinical audit; use of method assessing non-pertinent treatment is interesting too. Analysis of the non-conformities and gaps between theory and practice allows identifying various possible causes (professional, institutional, organizational or personal) in order to implement corrective action plans, in a logic of continuous improvement.

Contrast-enhanced harmonic endoscopic ultrasound in solid lesions of the pancreas: results of a pilot study

BACKGROUND AND STUDY AIMS

Distinguishing pancreatic adenocarcinoma from other pancreatic masses remains challenging with current imaging techniques. This prospective study aimed to evaluate the accuracy of a new procedure, imaging the microcirculation pattern of the pancreas by contrast-enhanced harmonic endoscopic ultrasound (CEH-EUS) with a new Olympus prototype echo endoscope.

PATIENTS AND METHODS

35 patients presenting with solid pancreatic lesions were prospectively enrolled. All patients had conventional B mode and power Doppler EUS. After an intravenous bolus injection of 2.4 ml of a second-generation ultrasound contrast agent (SonoVue) CEH-EUS was then performed with a new Olympus prototype echo endoscope (xGF-UCT 180). The microvascular pattern was compared with the final diagnosis based on the pathological examination of specimens from surgery or EUS-guided fine-needle aspiration (EUS-FNA) or on follow-up for at least 12 months.

RESULTS

The final diagnoses were: 18 adenocarcinomas, 9 neuroendocrine tumors, 7 chronic pancreatitis, and 1 stromal tumor. Power Doppler failed to display microcirculation, whereas harmonic imaging demonstrated it in all cases. Out of 18 lesions with a hypointense signal on CEH-EUS, 16 were adenocarcinomas. The sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and accuracy of hypointensity for diagnosing pancreatic adenocarcinoma were 89 %, 88 %, 88 %, 89 %, and 88.5 %, compared with corresponding values of 72 %, 100 %, 77 %, 100 %, and 86 % for EUS-FNA. Of five adenocarcinomas with false-negative results at EUS-FNA, four had a hypointense echo signal at CEH-EUS.

CONCLUSIONS

CEH-EUS with the new Olympus prototype device successfully visualizes the microvascular pattern in pancreatic solid lesions, and may be useful for distinguishing adenocarcinomas from other pancreatic masses.

Miniprobe EUS in the pretherapeutic assessment of early esophageal neoplasia

BACKGROUND AND STUDY AIMS

The high-frequency endosonography miniprobe has been advocated prior to endoscopic treatment of superficial esophageal neoplasm. We conducted a retrospective study, which summarized our clinical experience with various miniprobe techniques in the assessment of early squamous cell carcinoma (SCC) and superficial adenocarcinoma on Barrett's mucosa (SAB).

PATIENTS AND METHODS

A total of 106 superficial and naive esophageal lesions were included in this series (52 SAB, 54 SCC). The results of the miniprobe staging were compared with pathology in order to determine the accuracy of this technique in differentiating mucosal from submucosal infiltration. Secondary aims were a comparison between the frequencies (20- vs. 30-MHz) and coupling methods (water-filled lumen vs. balloon-sheathed catheter) used.

RESULTS

Overall accuracy, sensitivity, and specificity to differentiate T1sm from T1 m tumors were 73.5 %, 62 %, and 76.5 %, respectively. Overdiagnosis occurred in 18.6 % of the lesions. No statistically significant difference was found in the accuracy of the miniprobe staging between the two lesion types (SCC and SAB) ( P = 0.65), and results were significantly poorer in the distal part of the esophagus ( P = 0.00039). No significant difference was found between the two frequencies ( P = 0.51). Water-filled lumen proved to be superior to the balloon-sheathed catheter ( P = 0.015).

CONCLUSION

High-frequency miniprobe examination has a limited accuracy in the detection of submucosal invasion in early esophageal cancer. Further improvements in acoustic coupling and ultrasound technique are required to improve the miniprobe accuracy before its implementation into clinical routine.

Endoscopic mucosal resection for squamous premalignant and early malignant lesions of the esophagus

BACK AND STUDY AIMS: Endoscopic mucosal resection (EMR) is used to treat premalignant and malignant digestive tract lesions. This report presents the efficacy and safety of EMR for squamous superficial neoplastic esophageal lesions.

PATIENTS AND METHODS

A retrospective cohort study presented data from 51 patients with 54 lesions over an 8-year period, between November 1997 and September 2005. Dysplasas or mucosal (m) T1 carcinomas were treated with repeated EMR until there was a complete local remission. Patients with submucosal (sm) T1 carcinomas were treated with repeated EMR until there was a complete local remission. Patients with submucosal (sm) T1 carcinomas or more advanced stage were offered surgery or chemoradiotherapy.

RESULTS

There was no mortality, perforation, or major hemorrhage, and there were three easily dilated stenoses. Of the patients, 16 had lesions graded as T1sm or more advanced and one patient was found to have normal tissue post EMR. Complete local remission was achieved in 31 of the 34 patients with dysplasia or T1 m cancers (91%). There was no distant relapse and there was local disease recurrence in eight of the 31 patients (26%). The 5-year survival rate was 95%.

CONCLUSIONS

EMR for squamous superficial neoplastic lesions of the esophagus is safe and provides satisfactory survival results.

Dynamic MR urography in urinary tract obstruction: implementation and preliminary results

BACKGROUND

Recent studies have demonstrated magnetic resonance (MR) capabilities in evaluating renal morphology and function in patients with urinary obstruction. The objective of this report is to support the introduction of dynamic MR renography on any MR equipment.

METHODS

A custom-made device of vials filled with different concentrations of gadolinium was studied by combinations of T1-weighted gradient-echo sequences and coils. We compared the capabilities of two coils (phased array vs. standard body), the properties of dynamic sequences, and the effects of increasing concentrations of gadolinium on signal intensity. In a second section, we designed MR urography plug-ins of Image J (DICOM image software) for the analysis of dynamic studies.

RESULTS

Optimized gradient-echo sequences acquired with a phased array body coil produced acceptable quality images with a linear relation between signal intensity and the lowest concentrations of gadolinium. In vitro measurements showed loss of linearity above 8 mmol/L.

CONCLUSION

Theoretical calculation and data from the literature suggest that the gadolinium dose to the patient should not exceed one-fourth of the usual one (0.025 mmol/kg). Postprocessing using Image J software and the specifically designed plug-ins was validated. The collection of plug-ins is now available on the Internet.

Hypocaloric diet reduces exercise-induced alpha 2-adrenergic antilipolytic effect and alpha 2-adrenergic receptor mRNA levels in adipose tissue of obese women

Previous investigations have shown that alpha 2-adrenoceptor (alpha 2-AR) stimulation blunts lipid mobilization during physiological activation of the sympathetic nervous system promoted by exercise in sc abdominal adipose tissue (SCAAT) in obese men. To investigate the effect of a low calorie diet (LCD) on the alpha 2-adrenergic responsiveness and on the expression of alpha 2-AR and beta 2-adrenoceptor (beta 2-AR) in SCAAT, 11 obese women (weight: 99.1 +/- 4.6 kg; body mass index: 34.3 +/- 1.1 kg/m(2)) received a 12-wk diet providing 500 kcal/d less than their usual diet. The exercise-induced alpha 2-adrenergic antilipolytic effect was investigated in SCAAT before and at the end of LCD. Changes in extracellular glycerol concentration and local blood flow were measured in SCAAT during a 45-min exercise bout (50% of heart rate reserve) using a control microdialysis probe and a probe supplemented with the alpha2-AR antagonist phentolamine. SCAAT biopsies were performed for determination of mRNA levels using RT-competitive PCR. Plasma catecholamine responses to exercise bout were not different before and at the end of LCD. Before LCD, the exercise-induced increase in extracellular glycerol concentration was potentiated by phentolamine supplementation, while this potentiating effect of the alpha-antagonist was not observed at the end of LCD. No changes were observed for beta 2-AR and hormone-sensitive lipase mRNA levels, while alpha 2-AR mRNA level was significantly decreased in adipose tissue during LCD. These findings show that alpha 2-AR-mediated antilipolytic action is reduced by a moderate hypocaloric diet and that down-regulation of alpha 2-AR mRNA levels may participate in the decrease of the alpha 2-adrenergic effect revealed by microdialysis.

[Ischemic orchiditis: review of 5 cases diagnosed by color Doppler ultrasonography]

PURPOSE

To study color-doppler ultrasoundfeatures of testicular infarction caused by orchiepididymitis, a severe complication of orchiepididymitis.

MATERIAL

and Methods. Five patients were included over a 2 year period. All presented with more than 24 hours of pain. A final diagnosis of testicular infarction caused by orchiepididymitis and color doppler ultrasound was available in all cases.

RESULTS

All patients showed doppler ultrasound signs of testicular ischemia. Either vascularisation was not detectable or intratesticular resistive index was increased with a negative diastolic flow. Orchidectomy was performed in all patients.

CONCLUSION

Color doppler examination of the scrotum should include measurement of intratesticular resistive index. An elevated RI can be suggestive of ischemia.

[Cost of transfusion in AIDS. Experience at the Claude-Bernard Hospital apropos of 28 cases]

The study of 28 confirmed cases of AIDS shows that transfused patients use a large amount of hospital's blood products, especially platelets. For these patients, the average cost of transfusion is higher than that, for intensive care unit patient's. The use of irradiated products increases the cost (+ 35%). As there is a shortage of donors, if the present precautions are respected, there is no reason why the hospital should not continue to ask the patient's family and circle of friends, to donate blood.