bims-liverm 2023-01-08 papers

bims-liverm

Biomed News

on Liver Metabolism

Issue of 2023–01–08
seven papers selected by

Biological tuners to reshape the bile acid pool for therapeutic purposes in non-alcoholic fatty liver disease.
Liver-specific FGFR4 knockdown in mice on a HFD increases bile acid synthesis and improves hepatic steatosis.
The role of bile acid metabolism in the occurrence and development of NAFLD.
Establishment of an in vitro cholestasis risk assessment system using two-dimensional cultured HepaRG cells and 12 bile acids.
Effects of Biliary Phospholipids on Cholesterol Crystallization and Growth in Gallstone Formation.
Extracellular vesicles and insulin-mediated vascular function in metabolic syndrome.
Comparable Effects of Sleeve Gastrectomy and Roux-en-Y Gastric Bypass on Basal Fuel Metabolism and Insulin Sensitivity in Individuals with Obesity and Type 2 Diabetes.

Clin Sci (Lond). 2023 Jan 13. 137(1): 65-85

Biological tuners to reshape the bile acid pool for therapeutic purposes in non-alcoholic fatty liver disease.

Justine Gillard, Isabelle A Leclercq.

  Bile acids synthesized within the hepatocytes are transformed by gut microorganisms and reabsorbed into the portal circulation. During their enterohepatic cycling, bile acids act as signaling molecules by interacting with receptors to regulate pathways involved in many physiological processes. The bile acid pool, composed of a variety of bile acid species, has been shown to be altered in diseases, hence contributing to disease pathogenesis. Thus, understanding the changes in bile acid pool size and composition in pathological processes will help to elaborate effective pharmacological treatments. Five crucial steps along the enterohepatic cycle shape the bile acid pool size and composition, offering five possible targets for therapeutic intervention. In this review, we provide an insight on the strategies to modulate the bile acid pool, and then we discuss the potential benefits in non-alcoholic fatty liver disease.

Keywords:  bile acids; enterohepatic cycle; gut microbiota; non alcoholic fatty liver disease; non-alcoholic steatohepatitis

DOI:  https://doi.org/10.1042/CS20220697
J Lipid Res. 2022 Dec 28. pii: S0022-2275(22)00157-2. [Epub ahead of print] 100324

Liver-specific FGFR4 knockdown in mice on a HFD increases bile acid synthesis and improves hepatic steatosis.

Francois Moreau, Bruna Brasil Brunao, Xiang-Yu Liu, Frederic Tremblay, Kevin Fitzgerald, Julian Avila-Pacheco, Clary Clish, Ronald C Kahn, Samir Softic.

  Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease with increased risk in patients with metabolic syndrome. There are no FDA approved treatments, but farnesoid X receptor (FXR) agonists have shown promising results in clinical studies for NAFLD management. In addition to FXR, fibroblast growth factor receptor FGFR4 is a key mediator of hepatic bile acid synthesis. Using N-acetylgalactosamine-conjugated siRNA, we knocked down FGFR4 specifically in the liver of mice on chow or high-fat diet (HFD) and in mouse primary hepatocytes to determine the role of FGFR4 in metabolic processes and hepatic steatosis. Liver-specific FGFR4 silencing increased bile acid production and lowered serum cholesterol. Additionally, we found that HFD-induced liver steatosis and insulin resistance improved following FGFR4 knockdown. These improvements were associated with activation of the FXR-FGF15 axis in intestinal cells, but not in hepatocytes. We conclude that targeting FGFR4 in the liver to activate the intestinal FXR-FGF15 axis may be a promising strategy for the treatment of NAFLD and metabolic dysfunction.

Keywords:  IRS-1; Insulin Resistance; Liver; NAFLD; Obesity; bile acids; cholesterol; farnesoid X receptor; fibroblast growth factor receptor 4; liver steatosis

DOI:  https://doi.org/10.1016/j.jlr.2022.100324
Front Mol Biosci. 2022 ;9 1089359

The role of bile acid metabolism in the occurrence and development of NAFLD.

Hao Bing, Yi-Ling Li.

  Non-alcoholic fatty liver disease (NAFLD) has become one of the important causes of cirrhosis and liver cancer, resulting in a huge medical burden worldwide. Currently, effective non-invasive diagnostic indicators and drugs for NAFLD are still lacking. With the development of metabolomics technology, the changes in metabolites during the development of NAFLD have been gradually revealed. Bile acid (BA) is the main endpoint of cholesterol metabolism in the body. In addition, it also acts as a signaling factor to regulate metabolism and inflammation in the body through the farnesyl X receptor and G protein-coupled BA receptor. Studies have shown that BA metabolism is associated with the development of NAFLD, but a large number of animal and clinical studies are still needed. BA homeostasis is maintained through multiple negative feedback loops and the enterohepatic circulation of BA. Recently, treatment of NAFLD by interfering with BA synthesis and metabolism has become a new research direction. Here, we review the changes in BA metabolism and its regulatory mechanisms during the development of NAFLD and describe the potential of studies exploring novel non-invasive diagnostic indicators and therapeutic targets for NAFLD based on BA metabolism.

Keywords:  bile acid; farnesyl X receptor; gut microbiota; metabolomics; non-alcoholic fatty liver disease

DOI:  https://doi.org/10.3389/fmolb.2022.1089359
J Toxicol Sci. 2023 ;48(1): 47-56

Establishment of an in vitro cholestasis risk assessment system using two-dimensional cultured HepaRG cells and 12 bile acids.

Toshihisa Koga, Kenji Takeuchi, Ken Umehara.

  Drug-induced liver injury (DILI) is a major cause of market withdrawal or drug-development discontinuation because of safety concerns. In this study, we focused on drug-induced cholestasis (DIC) to establish an in vitro cytotoxicity test system and analyze its sensitivity using two-dimensional (2-D) cultured HepaRG cells and 12 types of bile acids (BAs) present in the human serum. First, to detect the cytotoxicity associated with cholestasis effectively, non-toxic BA concentrations were investigated and determined to be 100-fold the human serum value (455 μM total BAs). Next, the cytotoxicity of 31 compounds that can inhibit the bile acid export pump (BSEP) and were categorized as no-DILI-concern, less-DILI-concern, and most-DILI-concern was examined. None of the no-DILI-concern compounds yielded cytotoxicity, whereas almost all less-DILI-concern compounds (with the exception of simvastatin) and most-DILI-concern compounds (with the exception of bosentan) exhibited cytotoxicity. An investigation of the cause of cytotoxicity using 3H-taurocholic acid revealed that most-DILI-concern and less-DILI-concern compounds, but not no-DILI-concern compounds, triggered the accumulation of radioactivity in the cell lysates. Thus, the onset of cytotoxicity seemed to be associated with cholestasis. The established HepaRG cytotoxicity assessment system (sensitivity of 89%, specificity of 100%, and accuracy of 97%) was mostly superior to the Css/BSEP IC50 (> 0.1) assessment system (sensitivity of 83%, specificity of 100%, and accuracy of 72%). Therefore, the assay method using 2-D cultured HepaRG cells and 12 BAs established here can be widely applicable as a model for the in vitro potential assessment of DIC.

Keywords:  Bile Acids; Cholestasis; HepaRG cells

DOI:  https://doi.org/10.2131/jts.48.47
Adv Ther. 2023 Jan 05.

Effects of Biliary Phospholipids on Cholesterol Crystallization and Growth in Gallstone Formation.

Helen H Wang, Piero Portincasa, Min Liu, David Q-H Wang.

  The prevalence of cholesterol gallstone disease is increasing, primarily due to the global epidemic of obesity associated with insulin resistance, and this trend leads to a considerable healthcare, financial, and social burden worldwide. Although phospholipids play an essential role in maintaining cholesterol solubility in bile through both mixed micelles and vesicles, little attention has been paid to the impact of biliary phospholipids on the pathogenesis of cholesterol gallstone formation. A reduction or deficiency of biliary phospholipids results in a distinctly abnormal metastable physical-chemical state of bile predisposing to supersaturation with cholesterol. Changes in biliary phospholipid concentrations influence cholesterol crystallization by yielding both liquid crystalline and "anhydrous" crystalline metastable intermediates, evolving into classical parallelogram-shaped cholesterol monohydrate crystals in supersaturated bile. As a result, five distinct crystallization pathways, A-E, have been defined, mainly based on the prime habits of liquid and solid crystals in the physiological or pathophysiological cholesterol saturation of gallbladder and hepatic bile. This review concisely summarizes the chemical structures and physical-chemical properties of biliary phospholipids and their physiological functions in bile formation and cholesterol solubility in bile, as well as comprehensively discusses the latest advances in the role of biliary phospholipids in cholesterol crystallization and growth in gallstone formation, largely based on the findings from clinical and animal studies and in vitro experiments. The insights gleaned from uncovering the cholelithogenic mechanisms are expected to form a fundamental framework for investigating the hitherto elusive events in the earliest stage of cholesterol nucleation and crystallization. This may help to identify better measures for early diagnosis and prevention in susceptible subjects and effective treatment of patients with gallstones.

Keywords:  ABCB4 transporter; Bile acids; Bile formation; Biliary lipid secretion; Cholesterol crystallization; Liquid crystals; Lith genes; Micelles; Vesicles

DOI:  https://doi.org/10.1007/s12325-022-02407-8
Physiol Rep. 2023 Jan;11(1): e15530

Extracellular vesicles and insulin-mediated vascular function in metabolic syndrome.

Tristan J Ragland, Emily M Heiston, Anna Ballantyne, Nathan R Stewart, Sabrina La Salvia, Luca Musante, Melissa A Luse, Brant E Isakson, Uta Erdbrügger, Steven K Malin.

  Metabolic Syndrome (MetS) raises cardiovascular disease risk. Extracellular vesicles (EVs) have emerged as important mediators of insulin sensitivity, although few studies on vascular function exist in humans. We determined the effect of insulin on EVs in relation to vascular function. Adults with MetS (n = 51, n = 9 M, 54.8 ± 1.0 years, 36.4 ± 0.7 kg/m2 , ATPIII: 3.5 ± 0.1 a.u., VO2 max: 22.1 ± 0.6 ml/kg/min) were enrolled in this cross-sectional study. Peripheral insulin sensitivity (M-value) was determined during a euglycemic clamp (40 mU/m2 /min, 90 mg/dl), and blood was collected for EVs (CD105+, CD45+, CD41+, TX+, and CD31+; spectral flow cytometry), inflammation, insulin, and substrates. Central hemodynamics (applanation tonometry) was determined at 0 and 120 min via aortic waveforms. Pressure myography was used to assess insulin-induced arterial vasodilation from mouse 3rd order mesenteric arteries (100-200 μm in diameter) at 0.2, 2 and 20 nM of insulin with EVs from healthy and MetS adults. Adults with MetS had low peripheral insulin sensitivity (2.6 ± 0.2 mg/kg/min) and high HOMA-IR (4.7 ± 0.4 a.u.) plus Adipose-IR (13.0 ± 1.3 a.u.). Insulin decreased total/particle counts (p < 0.001), CD45+ EVs (p = 0.002), AIx75 (p = 0.005) and Pb (p = 0.04), FFA (p < 0.001), total adiponectin (p = 0.006), ICAM (p = 0.002), and VCAM (p = 0.03). Higher M-value related to lower fasted total EVs (r = -0.40, p = 0.004) while higher Adipose-IR associated with higher fasted EVs (r = 0.42, p = 0.004) independent of VAT. Fasting CD105+ and CD45+ derived total EVs correlated with fasting AIx75 (r = 0.29, p < 0.05) and Pb (r = 0.30, p < 0.05). EVs from MetS participants blunted insulin-induced vasodilation in mesenteric arteries compared with increases from healthy controls across insulin doses (all p < 0.005). These data highlight EVs as potentially novel mediators of vascular insulin sensitivity and disease risk.

Keywords:  augmentation index; inflammation; insulin resistance; obesity; pulse wave analysis; vasodilation

DOI:  https://doi.org/10.14814/phy2.15530
J Diabetes Res. 2022 ;2022 5476454

Comparable Effects of Sleeve Gastrectomy and Roux-en-Y Gastric Bypass on Basal Fuel Metabolism and Insulin Sensitivity in Individuals with Obesity and Type 2 Diabetes.

Katrine Brodersen, Michael F Nielsen, Bjørn Richelsen, Esben S Lauritzen, Einar Pahle, Jan Abrahamsen, Bolette Hartmann, Jens J Holst, Niels Møller.

Aim: Bariatric surgery improves insulin sensitivity and glucose tolerance in obese individuals with type 2 diabetes (T2D), but there is a lack of data comparing the underlying metabolic mechanisms after the 2 most common surgical procedures Roux-en-Y gastric bypass surgery (RYGB) and sleeve gastrectomy (SG). This study was designed to assess and compare the effects of RYGB and SG on fuel metabolism in the basal state and insulin sensitivity during a two-step euglycemic glucose clamp.
Materials and Methods: 16 obese individuals with T2D undergoing either RYGB (n = 9) or SG (n = 7) were investigated before and 2 months after surgery, and 8 healthy individuals without obesity and T2D served as controls. All underwent a 2 h basal study followed by a 5 h 2-step hyperinsulinemic euglycemic glucose clamp at insulin infusion rates of 0.5 and 1.0 mU/kg LBM/min.
Results: RYGB and SG induced comparable 15% weight losses, normalized HbA1c, fasting glucose, fasting insulin, and decreased energy expenditure. In parallel, we recorded similar increments (about 100%) in overall insulin sensitivity (M-value) and glucose disposal and similar decrements (about 50%) in endogenous glucose production and FFA levels during the clamp; likewise, basal glucose and insulin concentrations decreased proportionally.
Conclusion: Our data suggest that RYGB and SG improve basal fuel metabolism and two-step insulin sensitivity in the liver, muscle, and fat and seem equally favourable when investigated 2 months after surgery. This trial is registered with NCT02713555.

DOI: https://doi.org/10.1155/2022/5476454