Improvement of NASH and liver fibrosis through modulation of the gut-liver axis by a novel intestinal FXR agonist

Farnesoid X receptor (FXR) plays a pivotal role in the regulation of bile acid homeostasis and is involved in the pathogenesis of nonalcoholic steatohepatitis (NASH). Although FXR agonists effectively alleviate pathological features of NASH, adverse effects such as disturbance of cholesterol homeostasis and occurrence of pruritus remain to be addressed. Here, we identified a novel FXR agonist, ID119031166 (ID166), and explored the pharmacological benefits of ID166 in the treatment of NASH. ID166, a potent and selective non-bile acid FXR agonist, exhibits preferential distribution in the intestine and shows no agonist activity against potential itch receptors including Mas-related G protein-coupled receptor X4 (MRGPRX4). Interestingly, ID166 significantly attenuated total nonalcoholic fatty liver disease (NAFLD) activity and liver fibrosis in a free choice diet-induced NASH hamster model. In addition, ID166 drastically modulated the relative abundance of five gut microbes and reduced the increase in plasma total bile acid levels to normal levels in NASH hamsters. Moreover, long-term treatment with ID166 significantly improved key histological features of NASH and liver fibrosis in a diet-induced NASH mouse model. In the NASH mouse livers, RNA-seq analysis revealed that ID166 reduced the gene expression changes associated with both NASH and liver fibrosis. Notably, ID166 exhibited no substantial effects on scratching behavior and serum IL-31 levels in mice. Our findings suggest that ID166, a novel FXR agonist with improved pharmacological properties, provides a preclinical basis to optimize clinical benefits for NASH drug development.

Molecular imaging of liver inflammation using an anti-VCAM-1 nanobody

To date, a biopsy is mandatory to evaluate parenchymal inflammation in the liver. Here, we evaluated whether molecular imaging of vascular cell adhesion molecule-1 (VCAM-1) could be used as an alternative non-invasive tool to detect liver inflammation in the setting of chronic liver disease. To do so, we radiolabeled anti-VCAM-1 nanobody (99mTc-cAbVCAM1-5) and used single-photon emission computed tomography (SPECT) to quantify liver uptake in preclinical models of non-alcoholic fatty liver disease (NAFLD) with various degree of liver inflammation: wild-type mice fed a normal or high-fat diet (HFD), FOZ fed a HFD and C57BL6/J fed a choline-deficient or -supplemented HFD. 99mTc-cAbVCAM1-5 uptake strongly correlates with liver histological inflammatory score and with molecular inflammatory markers. The diagnostic power to detect any degree of liver inflammation is excellent (AUROC 0.85-0.99). These data build the rationale to investigate 99mTc-cAbVCAM1-5 imaging to detect liver inflammation in patients with NAFLD, a largely unmet medical need.

Enhancing NO pathway improves diastolic function in a hamster model of heart failure with preserved ejection fraction associated with nonalcoholic steatohepatitis

Background and aims

Heart failure with preserved ejection fraction (HFpEF) is a complex clinical phenotype frequently associated to the presence of multiple non-cardiac comorbidities including nonalcoholic steatohepatitis (NASH) commonly seen in metabolic syndrome and obesity. In this context, the enhanced production of ROS due to systemic inflammatory state participates to the myocardial structural and functional alterations by limiting nitric oxide bioavailability. We thus evaluated the effect of the phosphodiesterase type 5 (PDE5) inhibitor, vardenafil, on cardiac function and remodeling in a NASH hamster model.

Method

Male Golden Syrian hamsters were fed for 20 weeks with a free choice diet consisting in free access to control chow diet with normal drinking water or a high fat/high cholesterol diet with 10% fructose enriched drinking water. At 15 weeks hamsters were randomized on E/A ratio and ejection fraction to receive either vardenafil (10mg/kg/day orally for 5 weeks) or vehicle before cardiac and metabolic parameters evaluation.

Results

After 20 weeks of free choice diet, hamsters presented a large increase in hepatic lipid contents and developed NASH. Echocardiography showed that systolic function was preserved with ejection fraction in normal range whatever the diet. In contrast, E/A ratio was significantly increased in free choice fed hamsters (2,1±0,1 vs 1,4±0,04) and E'/A' ratio inverted when compared to control (0,8±0,02 vs 1,3±0,04). This was associated with a decreased isovolumic relaxation time (IVRT) and an increased E/E' ratio signing relaxation impairment and higher filling pressure, respectively. Moreover, pro-BNP was largely increased in free choice fed hamsters when compared to controls. While vardenafil had no impact on NASH, diastolic function was largely improved as evidenced by the significant decrease in E/A and E/E' ratios along with the increase in E'/A' ratio and IVRT. This effect was corroborated by the normalization of the pro-BNP plasma levels induced by the 5 week-treatment with vardenafil.

Conclusion

The present data demonstrate that free choice fed hamsters developed NASH and showed the ultimate stage of diastolic dysfunction characterized by a restrictive profile combining compliance and relaxation impairments as well as higher filling pressure. While no effect on NASH was observed, enhancing NO pathway with vardenafil treatment significantly improves diastolic function in this hamster model of HFpEF.

Funding Acknowledgement

Type of funding sources: None.

A promising rat model of heart failure with preserved ejection fraction associated to multiple comorbidities

Background and aims

Heart failure with preserved ejection fraction (HFpEF) is a complex clinical phenotype often associated to the presence of multiple non-cardiac interrelated comorbidities including diabetes, obesity, hypertension. A major challenge in the development of new therapies for HFpEF is the lack of animal models that truly recapitulate the complexities of the disease. One promising candidate is the Lund MetS rat, a congenic BBDR.cg-lepr.cp model generated by introgression of the Koletsky leptin receptor mutation into the BioBreeding Diabetes Resistant (BBDR) rat.

Methods

14-week-old Lund MetS obese T2D rats were exposed to salt enriched diet (0.8% NaCl in diet) for 6 weeks. Age-matched lean rats (ctrl) were fed a normal chow diet. Cardiovascular phenotyping was assessed by echocardiography and blood pressure measurement. Vascular function of isolated thoracic aortas, as well as kidney and cardiac parameters were also evaluated at the end of the 6-week diet period.

Results

After 6-week enriched salt diet period, mean arterial pressure increased from 120mmHg to 160mmHg (vs 100mmHg in chow-fed lean rat). The hypertensive state also led to renal hypertrophy with up to a 2-fold higher kidney weights. Echocardiography showed a preserved systolic function with quite similar ejection fraction and fractional shortening in Lund MetS and lean rats. In contrast, high salt-fed Lund MetS rats developed cardiac hypertrophy confirmed by a large increase in heart, left ventricle, and left atria weights as compared to lean rats. Diastolic dysfunction was also highlighted with inverted E/A and E'/A' ratios along with a prolongation of the isovolumic relaxation time (IVRT). This was accompanied by an increase in circulating levels of soluble ST2 and NT- proBNP. Finally, aortic rings assays showed that both endothelium dependent and independent vasodilating properties were impaired in the high salt-fed Lund MetS rats.

Conclusions

The present data demonstrate that the Lund MetS rat fed a high salt diet developed a marked hypertension, pathological cardiac remodeling and diastolic dysfunction without modification of ejection fraction, along with obesity and type 2 diabetes. Thus, this could be a relevant model to bring forward effective new treatments for HFpEF patients.

Funding Acknowledgement

Type of funding sources: None.

Diet-Induced Obesity and NASH Impair Disease Recovery in SARS-CoV-2-Infected Golden Hamsters

Obese patients with non-alcoholic steatohepatitis (NASH) are prone to severe forms of COVID-19. There is an urgent need for new treatments that lower the severity of COVID-19 in this vulnerable population. To better replicate the human context, we set up a diet-induced model of obesity associated with dyslipidemia and NASH in the golden hamster (known to be a relevant preclinical model of COVID-19). A 20-week, free-choice diet induces obesity, dyslipidemia, and NASH (liver inflammation and fibrosis) in golden hamsters. Obese NASH hamsters have higher blood and pulmonary levels of inflammatory cytokines. In the early stages of a SARS-CoV-2 infection, the lung viral load and inflammation levels were similar in lean hamsters and obese NASH hamsters. However, obese NASH hamsters showed worse recovery (i.e., less resolution of lung inflammation 10 days post-infection (dpi) and lower body weight recovery on dpi 25). Obese NASH hamsters also exhibited higher levels of pulmonary fibrosis on dpi 25. Unlike lean animals, obese NASH hamsters infected with SARS-CoV-2 presented long-lasting dyslipidemia and systemic inflammation. Relative to lean controls, obese NASH hamsters had lower serum levels of angiotensin-converting enzyme 2 activity and higher serum levels of angiotensin II—a component known to favor inflammation and fibrosis. Even though the SARS-CoV-2 infection resulted in early weight loss and incomplete body weight recovery, obese NASH hamsters showed sustained liver steatosis, inflammation, hepatocyte ballooning, and marked liver fibrosis on dpi 25. We conclude that diet-induced obesity and NASH impair disease recovery in SARS-CoV-2-infected hamsters. This model might be of value for characterizing the pathophysiologic mechanisms of COVID-19 and evaluating the efficacy of treatments for the severe forms of COVID-19 observed in obese patients with NASH.

Alteration of the gut microbiota's composition and metabolic output correlates with COVID-19-like severity in obese NASH hamsters

Obese patientss with nonalcoholic steatohepatitis (NASH) are particularly prone to developing severe forms of coronavirus disease 19 (COVID-19). The gut-to-lung axis is critical during viral infections of the respiratory tract, and a change in the gut microbiota's composition might have a critical role in disease severity. Here, we investigated the consequences of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on the gut microbiota in the context of obesity and NASH. To this end, we set up a nutritional model of obesity with dyslipidemia and NASH in the golden hamster, a relevant preclinical model of COVID-19. Relative to lean non-NASH controls, obese NASH hamsters develop severe inflammation of the lungs and liver. 16S rRNA gene profiling showed that depending on the diet, SARS-CoV-2 infection induced various changes in the gut microbiota's composition. Changes were more prominent and transient at day 4 post-infection in lean animals, alterations still persisted at day 10 in obese NASH animals. A targeted, quantitative metabolomic analysis revealed changes in the gut microbiota's metabolic output, some of which were diet-specific and regulated over time. Our results showed that specifically diet-associated taxa are correlated with disease parameters. Correlations between infection variables and diet-associated taxa highlighted a number of potentially protective or harmful bacteria in SARS-CoV-2-infected hamsters. In particular, some taxa in obese NASH hamsters (e.g. Blautia and Peptococcus) were associated with pro-inflammatory parameters in both the lungs and the liver. These taxon profiles and their association with specific disease markers suggest that microbial patterns might influence COVID-19 outcomes.

Alteration of the gut microbiota following SARS-CoV-2 infection correlates with disease severity in hamsters

Mounting evidence suggests that the gut-to-lung axis is critical during respiratory viral infections. We herein hypothesized that disruption of gut homeostasis during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection may associate with early disease outcomes. To address this question, we took advantage of the Syrian hamster model. Our data confirmed that this model recapitulates some hallmark features of the human disease in the lungs. We further showed that SARS-CoV-2 infection associated with mild intestinal inflammation, relative alteration in intestinal barrier property and liver inflammation and altered lipid metabolism. These changes occurred concomitantly with an alteration of the gut microbiota composition over the course of infection, notably characterized by a higher relative abundance of deleterious bacterial taxa such as Enterobacteriaceae and Desulfovibrionaceae. Conversely, several members of the Ruminococcaceae and Lachnospiraceae families, including bacteria known to produce the fermentative products short-chain fatty acids (SCFAs), had a reduced relative proportion compared to non-infected controls. Accordingly, infection led to a transient decrease in systemic SCFA amounts. SCFA supplementation during infection had no effect on clinical and inflammatory parameters. Lastly, a strong correlation between some gut microbiota taxa and clinical and inflammation indices of SARS-CoV-2 infection severity was evidenced. Collectively, alteration of the gut microbiota correlates with disease severity in hamsters making this experimental model valuable for the design of interventional, gut microbiota-targeted, approaches for the control of COVID-19.Abbreviations: SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; COVID-19, coronavirus disease 2019; SCFAs, short-chain fatty acids; dpi, day post-infection; RT-PCR, reverse transcription polymerase chain reaction; IL, interleukin. ACE2, angiotensin converting enzyme 2; TMPRSS2, transmembrane serine protease 2.

Effects of excessive sodium chloride loading in the spontaneously diabetic torii (SDT) fatty rats, a preclinical model of type 2 diabetes mellitus

Type 2 diabetes mellitus represents an international health concern with its growing number of patients worldwide. At the same time, excessive salt consumption is also seen as a major cause of diseases such as hypertension and may expedite renal complications in diabetic patients. In this study, we investigated the effects of excessive sodium chloride supplementation on the kidney of the Spontaneously Diabetic Torii-Lepr^fa (SDT fatty) rat, an obese type 2 diabetes model. Male and female SDT fatty rats and normal Sprague-Dawley (SD) rats at 5 weeks of age were loaded with 0.3% sodium chloride (NaCl) in drinking water for 13 weeks. Blood serum and urinary parameters were observed throughout the experiment and kidney samples were examined in histopathological and genetical analyses. Significant changes on the body weight, blood pressure, urine volume, creatinine clearance, blood urea nitrogen (BUN), relative gene expressions of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), monocyte chemotactic protein-1 (MCP-1) and transforming growth factor-β (TGF-β) were observed in the salt-loaded male SDT fatty rats. Urinary L-type fatty acid-binding protein (L-FABP) and albumin levels were higher observed in the salt-loaded male SDT fatty rats throughout the period, but urinary albumin levels in the female SDT fatty rats remain unchanged. In the kidney, slight Armani-Ebstein changes, tubular degeneration, hyaline cast, and inflammatory cell infiltration were observed in female SDT fatty rats while the levels of some changes were higher in the salt-loaded group. The kidney of the salt-loaded male SDT fatty rats demonstrated a higher degree of lesions compared to the female group and the male unloaded group. Histopathological changes in salt-loaded SDT fatty rats show that excessive salt consumption may act as a diabetic pathology exacerbation factor, but the pathology may be influenced by gender difference. Urinary L-FABP levels may act as a useful biomarker to detect slight tubular damages in the kidney. Excessive salt loading was shown to exacerbate the renal injury in SDT fatty rats.

Elafibranor improves diet-induced nonalcoholic steatohepatitis associated with heart failure with preserved ejection fraction in Golden Syrian hamsters

BACKGROUND

Cardiovascular disease is the leading cause of deaths in nonalcoholic steatohepatitis (NASH) patients. Mouse models, while widely used for drug development, do not fully replicate human NASH nor integrate the associated cardiac dysfunction, i.e. heart failure with preserved ejection fraction (HFpEF). To overcome these limitations, we established a nutritional hamster model developing both NASH and HFpEF. We then evaluated the effects of the dual peroxisome proliferator activated receptor alpha/delta agonist elafibranor developed for the treatment of NASH patients.

METHODS

Male Golden Syrian hamsters were fed for 10 to 20 weeks with a free choice diet, which presents hamsters with a choice between control chow diet with normal drinking water or a high fat/high cholesterol diet with 10% fructose enriched drinking water. Biochemistry, histology and echocardiography analysis were performed to characterize NASH and HFpEF. Once the model was validated, elafibranor was evaluated at 15 mg/kg/day orally QD for 5 weeks.

RESULTS

Hamsters fed a free choice diet for up to 20 weeks developed NASH, including hepatocyte ballooning (as confirmed with cytokeratin-18 immunostaining), bridging fibrosis, and a severe diastolic dysfunction with restrictive profile, but preserved ejection fraction. Elafibranor resolved NASH, with significant reduction in ballooning and fibrosis scores, and improved diastolic dysfunction with significant reduction in E/A and E/E' ratios.

CONCLUSION

Our data demonstrate that the free choice diet induced NASH hamster model replicates the human phenotype and will be useful for validating novel drug candidates for the treatment of NASH and associated HFpEF.

Ezetimibe Enhances Macrophage-to-Feces Reverse Cholesterol Transport in Golden Syrian Hamsters Fed a High-Cholesterol Diet

The aim of this work was to evaluate reverse cholesterol transport (RCT) in hamster, animal model expressing CETP under a high cholesterol diet (HF) supplemented with Ezetimibe using primary labelled macrophages. We studied three groups of hamsters (n=8/group) for 4 weeks: 1) chow diet group: Chow, 2) High cholesterol diet group: HF and 3) HF group supplemented with 0.01% of ezetimibe: HF+0.01%Ezet. Following intraperitoneal injection of ³H-cholesterol-labelled hamster primary macrophages, we measured the in vivo macrophage-to-feces RCT. .HF group exhibited an increase of triglycerides (TG), cholesterol, glucose in plasma and higher TG and cholesterol content in liver (p<0.01) compared to Chow group. Ezetimibe induced a significant decrease in plasma cholesterol with a lower LDL and VLDL cholesterol (p<0.001) and in liver cholesterol (p<0.001) and TG (p<0.01) content compared to HF. In vivo RCT essay showed an increase of tracer level in plasma and liver (p<0.05) but not in feces in HF compared to Chow group. The amount of labelled total sterol and cholesterol in liver and feces was significantly reduced (p<0.05) and increased (p=0.05) respectively with Ezetimibe treatment. No significant increase was obtained for labelled feces bile acids in HF+0.01%Ezet compared to HF. Ezetimibe decreased SCD1 gene expression and increased SR-B1 (p<0.05) in liver but did not affect NPC1L1 nor ABCG5 and ABCG8 expression in jejunum. In conclusion, ezetimibe exhibited an atheroprotective effect by enhancing RCT in hamster and decreasing LDL cholesterol. Ours findings showed also a hepatoprotective effect of ezetimibe by decreasing hepatic fat content. Significance Statement This work was assessed to determine the effect of ezetimibe treatment on high cholesterol diet induced disturbances and especially the effect on reverse cholesterol transport in animal model with CETP activity and using labelled primary hamster macrophages. We were able to demonstrate that ezetimibe exhibited an atheroprotective effect by enhancing RCT and by decreasing LDL cholesterol in hamster. We showed also a hepatoprotective effect of ezetimibe by decreasing hepatic fat content.

A 3-week nonalcoholic steatohepatitis mouse model shows elafibranor benefits on hepatic inflammation and cell death

The long duration of animal models represents a clear limitation to quickly evaluate the efficacy of drugs targeting nonalcoholic steatohepatitis (NASH). We, therefore, developed a rapid mouse model of liver inflammation (i.e., the mouse fed a high-fat/high-cholesterol diet, where cyclodextrin is co-administered to favor hepatic cholesterol loading, liver inflammation, and NASH within 3 weeks), and evaluated the effects of the dual peroxisome proliferator-activated receptor alpha/delta agonist elafibranor (ELA). C57BL6/J mice were fed a 60% high-fat, 1.25% cholesterol, and 0.5% cholic acid diet with 2% cyclodextrin in drinking water (HFCC/CDX diet) for 3 weeks. After 1 week of the diet, mice were treated orally with vehicle or ELA 20 mg/kg q.d. for 2 weeks. Compared with vehicle, ELA markedly reduced liver lipids and nonalcoholic fatty liver disease activity scoring, through steatosis, inflammation, and fibrosis (all P < 0.01 vs. vehicle). Flow cytometry analysis showed that ELA significantly improved the HFCC/CDX diet-induced liver inflammation by preventing the increase in total number of immune cells (CD45+), Kupffer cells, dendritic cells, and monocytes population, as well as the reduction in natural killer and natural killer T cells, and by blocking conversion of T cells in regulatory T cells. ELA did not alter pyroptosis (Gasdermin D), but significantly reduced necroptosis (cleaved RIP3) and apoptosis (cleaved caspase 3) in the liver. In conclusion, ELA showed strong benefits on NASH, including improvement in hepatic inflammation, necroptosis, and apoptosis in the 3-week NASH mouse. This preclinical model will be useful to rapidly detect the effects of novel drugs targeting NASH.

Liraglutide improves hepatic steatosis and metabolic dysfunctions in a 3-week dietary mouse model of nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is an emerging health problem worldwide. However, efficacious pharmacological treatment for NASH is lacking. A major issue for preclinical evaluation of potential therapeutics for NASH is the limited number of appropriate animal models, i.e., models that do not require long-term dietary intervention and adequately mimic disease progression in humans. The present study aimed to evaluate a 3-wk dietary mouse model of NASH and validate it by studying the effects of liraglutide, a compound in advanced clinical development for NASH. C57BL6/J mice were fed a diet high in fat (60%), cholesterol (1.25%), and cholic acid (0.5%), along with 2% hydroxypropyl-β-cyclodextrin in drinking water (HFCC-CDX diet). Histological and biological parameters were measured at 1 and 3 wk. After 1-wk diet induction, liraglutide was administrated daily for 2 wk and then NASH-associated phenotypic aspects were evaluated in comparison with control mice. Prior to treatment with liraglutide, mice fed the HFCC-CDX diet for 1 wk developed liver steatosis and had increased levels of oxidative-stress markers and hepatic and systemic inflammation. For mice not treated with liraglutide, these aspects were even more pronounced after 3 wk of the dietary period, with additional liver insulin resistance and fibrosis. Liraglutide treatment corrected the diet-induced alterations in glucose metabolism and significantly reduced hepatic steatosis and inflammation. This study provides a novel 3-wk dietary model of mice that rapidly develop NASH features, and this model will be suitable for evaluating the therapeutic efficacy of compounds in preclinical drug development for NASH.NEW & NOTEWORTHY We propose a diet high in fat (60%), cholesterol (1.25%), and cholic acid (0.5%) along with 2% hydroxypropyl-β-cyclodextrin in drinking water (HFCC-CDX diet) as a new dietary model of nonalcoholic steatohepatitis. We used the HFCC-CDX model to reproduce the main features of disease development in humans for the purpose of facilitating the rapid screening of drug candidates and prioritizing the more promising candidates for advanced preclinical assessment and subsequent clinical trials.

Saccharomyces boulardii CNCM I-745 changes lipidemic profile and gut microbiota in a hamster hypercholesterolemic model

Hypercholesterolemia is a main risk factor of cardiovascular disease. Probiotics are a safe approach to reduce elevated cholesterol without any deleterious effect to human health. Saccharomyces boulardii CNCM I-745 probiotic properties are well documented in a context of intestinal dysbiosis. Recent in vitro and preclinical studies have suggested its potential effects on dyslipidemia. This is the first controlled study investigating the effects of S. boulardii CNCM I-745 on lipidemic profile and gut microbiota in a hamster hypercholesterolemic model. Daily administration (3 g/kg) of S. boulardii for 21 or 39 days in hamsters fed a 0.3% cholesterol-diet significantly reduced total plasma cholesterol (P<0.001) and increased faecal total cholesterol (P<0.05) compared to vehicle-treated animals. S. boulardii significantly modified the gut microbiota composition of the hamster fed a 0.3% cholesterol-diet. These microbial abundancy modifications of the microbiota were correlated to variations of lipidemic values or liver genes expressions. In particularly we found that abundance of g_Allobaculum, the most modified taxon after S. boulardii treatment (+236%; P<0.05), was correlated to variations in plasmatic lipoproteins level and ABCG5 hepatic gene expression. We also observed a not previously described correlation between the levels of g_Oxalobacter in the gut microbiota and total cholesterol plasma concentration. In conclusion, we confirmed the cholesterol-lowering effects of S. boulardii intake and we demonstrated for the first time the S. boulardii effect on gut microbiota in the context of hypercholesterolemia in hamsters. Our results provide new insights for a beneficial and safe approach of hypercholesterolemia treatment and could be considered for clinical development, alone or in addition to conventional treatment.

Artemisinins Target GABAA Receptor Signaling and Impair α Cell Identity

Type 1 diabetes is characterized by the destruction of pancreatic β cells, and generating new insulin-producing cells from other cell types is a major aim of regenerative medicine. One promising approach is transdifferentiation of developmentally related pancreatic cell types, including glucagon-producing α cells. In a genetic model, loss of the master regulatory transcription factor Arx is sufficient to induce the conversion of α cells to functional β-like cells. Here, we identify artemisinins as small molecules that functionally repress Arx by causing its translocation to the cytoplasm. We show that the protein gephyrin is the mammalian target of these antimalarial drugs and that the mechanism of action of these molecules depends on the enhancement of GABA_A receptor signaling. Our results in zebrafish, rodents, and primary human pancreatic islets identify gephyrin as a druggable target for the regeneration of pancreatic β cell mass from α cells.

•

Artemisinins inhibit ARX function and impair α cell identity

•

Compounds act by stabilizing gephyrin, thus enhancing GABA_A receptor signaling

•

Artemisinins increase β cell mass in zebrafish and rodent models

•

Functional and transcriptional data indicate a conserved phenotype in human islets

Empagliflozin, via Switching Metabolism Toward Lipid Utilization, Moderately Increases LDL Cholesterol Levels Through Reduced LDL Catabolism

In clinical trials, a small increase in LDL cholesterol has been reported with sodium-glucose cotransporter 2 (SGLT2) inhibitors. The mechanisms by which the SGLT2 inhibitor empagliflozin increases LDL cholesterol levels were investigated in hamsters with diet-induced dyslipidemia. Compared with vehicle, empagliflozin 30 mg/kg/day for 2 weeks significantly reduced fasting blood glucose by 18%, with significant increase in fasting plasma LDL cholesterol, free fatty acids, and total ketone bodies by 25, 49, and 116%, respectively. In fasting conditions, glycogen hepatic levels were further reduced by 84% with empagliflozin, while 3-hydroxy-3-methylglutaryl-CoA reductase activity and total cholesterol hepatic levels were 31 and 10% higher, respectively (both P < 0.05 vs. vehicle). A significant 20% reduction in hepatic LDL receptor protein expression was also observed with empagliflozin. Importantly, none of these parameters were changed by empagliflozin in fed conditions. Empagliflozin significantly reduced the catabolism of (3)H-cholesteryl oleate-labeled LDL injected intravenously by 20%, indicating that empagliflozin raises LDL levels through reduced catabolism. Unexpectedly, empagliflozin also reduced intestinal cholesterol absorption in vivo, which led to a significant increase in LDL- and macrophage-derived cholesterol fecal excretion (both P < 0.05 vs. vehicle). These data suggest that empagliflozin, by switching energy metabolism from carbohydrate to lipid utilization, moderately increases ketone production and LDL cholesterol levels. Interestingly, empagliflozin also reduces intestinal cholesterol absorption, which in turn promotes LDL- and macrophage-derived cholesterol fecal excretion.

Probiotic B420 and prebiotic polydextrose improve efficacy of antidiabetic drugs in mice

BACKGROUND

Gut microbiota is now known to control glucose metabolism. Previous studies have shown that probiotics and prebiotics may improve glucose metabolism, but their effects have not been studied in combination with drug therapy. The aim of this study was to investigate whether probiotics and prebiotics combined with drug therapy affect diabetic outcomes.

METHODS

Two different study designs were used to test gut microbiota modulating treatments with metformin (MET) or sitagliptin (SITA) in male C57Bl/6J mice. In Design 1, diabetes was induced with four-week feeding with a ketogenic, 72 kcal% fat diet with virtually no carbohydrates. Mice were then randomly divided into four groups (n = 10 in each group): (1) vehicle, (2) Bifidobacterium animalis ssp. lactis 420 (B420) (10(9) CFU/day), (3) MET (2 mg/mL in drinking water), or (4) MET + B420 (same doses as in the MET and B420 groups). After another 4 weeks, glucose metabolism was assessed with a glucose tolerance test. Fasting glucose, fasting insulin and HOMA-IR were also assessed. In Design 2, mice were fed the same 72 kcal% fat diet to induce diabetes, but they were simultaneously treated within their respective groups (n = 8 in each group): (1) non-diabetic healthy control, (2) vehicle, (3) SITA [3 mg/(kg*day)] (4) SITA with prebiotic polydextrose (PDX) (0.25 g/day), (5) SITA with B420 (10(9) CFU/day), and (6) SITA + PDX + B420. Glucose metabolism was assessed at 4 weeks, and weight development was monitored for 6 weeks.

RESULTS

In Design 1, with low-dose metformin, mice treated with B420 had a significantly lower glycemic response (area under the curve) (factorial experiment, P = 0.002) and plasma glucose concentration (P = 0.02) compared to mice not treated with B420. In Design 2, SITA + PDX reduced glycaemia in the oral glucose tolerance test significantly more than SITA only (area under the curve reduced 28 %, P < 0.0001). In addition, B420, PDX or B420+PDX, together with SITA, further decreased fasting glucose concentrations compared to SITA only (-19.5, -40 and -49 %, respectively, P < 0.01 for each comparison). The effect of PDX may be due to its ability to increase portal vein GLP-1 concentrations together with SITA (P = 0.0001 compared to vehicle) whereas SITA alone had no statistically significant effect compared to vehicle (P = 0.14).

CONCLUSIONS

This study proposes that combining probiotics and/or prebiotics with antidiabetic drugs improves glycemic control and insulin sensitivity in mice. Mechanisms could be related to incretin secretion.

Anacetrapib and dalcetrapib differentially alters HDL metabolism and macrophage-to-feces reverse cholesterol transport at similar levels of CETP inhibition in hamsters

Cholesteryl ester transfer protein (CETP) inhibitors dalcetrapib and anacetrapib differentially alter LDL- and HDL-cholesterol levels, which might be related to the potency of each drug to inhibit CETP activity. We evaluated the effects of both drugs at similar levels of CETP inhibition on macrophage-to-feces reverse cholesterol transport (RCT) in hamsters. In normolipidemic hamsters, both anacetrapib 30 mg/kg QD and dalcetrapib 200 mg/kg BID inhibited CETP activity by ~60%. After injection of 3H-cholesteryl oleate labeled HDL, anacetrapib and dalcetrapib reduced HDL-cholesteryl esters fractional catabolic rate (FCR) by 30% and 26% (both P<0.001 vs. vehicle) respectively, but only dalcetrapib increased HDL-derived 3H-tracer fecal excretion by 30% (P<0.05 vs. vehicle). After 3H-cholesterol labeled macrophage intraperitoneal injection, anacetrapib stimulated 3H-tracer appearance in HDL, but both drugs did not promote macrophage-derived 3H-tracer fecal excretion. In dyslipidemic hamsters, both anacetrapib 1 mg/kg QD and dalcetrapib 200 mg/kg BID inhibited CETP activity by ~65% and reduced HDL-cholesteryl ester FCR by 36% (both P<0.001 vs. vehicle), but only anacetrapib increased HDL-derived 3H-tracer fecal excretion significantly by 39%. After 3H-cholesterol labeled macrophage injection, only anacetrapib 1 mg/kg QD stimulated macrophage-derived 3H-tracer appearance in HDL. These effects remained weaker than those observed with anacetrapib 60 mg/kg QD, which induced a maximal inhibition of CETP and stimulation of macrophage-derived 3H-tracer fecal excretion. In contrast, dalcetrapib 200 mg/kg BID reduced macrophage-derived 3H-tracer fecal excretion by 23% (P<0.05 vs. vehicle). In conclusion, anacetrapib and dalcetrapib differentially alter HDL metabolism and RCT in hamsters. A stronger inhibition of CETP may be required to promote macrophage-to-feces reverse cholesterol transport in dyslipidemic hamsters.

Raising HDL with CETP inhibitor torcetrapib improves glucose homeostasis in dyslipidemic and insulin resistant hamsters

We investigated whether raising HDL-cholesterol levels with cholesteryl ester transfer protein (CETP) inhibition improves glucose homeostasis in dyslipidemic and insulin resistant hamsters. Compared with vehicle, torcetrapib 30 mg/kg/day (TOR) administered for 10 days significantly increased by ∼40% both HDL-cholesterol levels and 3H-tracer appearance in HDL after 3H-cholesterol labeled macrophages i.p. injection. TOR significantly reduced fasting plasma triglycerides, glycerol and free fatty acids levels by 65%, 31% and 23%, respectively. TOR also reduced blood glucose levels and plasma insulin by 20% and 49% respectively, which led to a 60% reduction in HOMA-IR index (all p<0.01). After 3H-2-deoxyglucose and insulin injection, TOR significantly increased glucose uptake in oxidative soleus muscle, liver and heart by 26, 33 and 70%, respectively. Raising HDL levels with the CETP inhibitor torcetrapib improves glucose homeostasis in dyslipidemic and insulin resistant hamsters. Whether similar effect would be observed with other CETP inhibitors should be investigated.

Upregulating Reverse Cholesterol Transport With Cholesteryl Ester Transfer Protein Inhibition Requires Combination With the LDL-Lowering Drug Berberine in Dyslipidemic Hamsters

Objective—

This study aimed to investigate whether cholesteryl ester transfer protein inhibition promotes in vivo reverse cholesterol transport in dyslipidemic hamsters.

Methods and Results—

In vivo reverse cholesterol transport was measured after an intravenous injection of 3 H-cholesteryl-oleate–labeled/oxidized low density lipoprotein particles ( 3 H-oxLDL), which are rapidly cleared from plasma by liver-resident macrophages for further 3 H-tracer egress in plasma, high density lipoprotein (HDL), liver, and feces. A first set of hamsters made dyslipidemic with a high-fat and high-fructose diet was treated with vehicle or torcetrapib 30 mg/kg (TOR) over 2 weeks. Compared with vehicle, TOR increased apolipoprotein E–rich HDL levels and significantly increased 3 H-tracer appearance in HDL by 30% over 72 hours after 3 H-oxLDL injection. However, TOR did not change 3 H-tracer recovery in liver and feces, suggesting that uptake and excretion of cholesterol deriving from apolipoprotein E-rich HDL is not stimulated. As apoE is a potent ligand for the LDL receptor, we next evaluated the effects of TOR in combination with the LDL-lowering drug berberine, which upregulates LDL receptor expression in dyslipidemic hamsters. Compared with TOR alone, treatment with TOR+berberine 150 mg/kg resulted in lower apolipoprotein E–rich HDL levels. After 3 H-oxLDL injection, TOR+berberine significantly increased 3 H-tracer appearance in fecal cholesterol by 109%.

Conclusion—

Our data suggest that cholesteryl ester transfer protein inhibition alone does not stimulate reverse cholesterol transport in dyslipidemic hamsters and that additional effects mediated by the LDL-lowering drug berberine are required to upregulate this process.

Sitagliptin promotes macrophage-to-faeces reverse cholesterol transport through reduced intestinal cholesterol absorption in obese insulin resistant CETP-apoB100 transgenic mice

Dipeptidyl peptidase-4 inhibitors (DPP-4i) improve glycaemic control in type 2 diabetes, but their benefits on reverse cholesterol transport (RCT) remain unknown. We evaluated the effects of DPP-4i sitagliptin 500 mg/kg/day on RCT in obese insulin-resistant CETP-apoB100 transgenic mice. Metformin 300 mg/kg/day orally was used as a reference compound. Both metformin and sitagliptin showed the expected effects on glucose parameters. Although no significant effect was observed on total cholesterol and high-density lipoprotein (HDL) cholesterol levels, sitagliptin, but not metformin, increased faecal cholesterol mass excretion by 132% (p < 0.001 vs. vehicle), suggesting a potent effect on cholesterol metabolism. Mice were then injected i.p. with (3) H-cholesterol labelled macrophages to measure RCT over 48 h. Compared with vehicle, sitagliptin significantly increased macrophage-derived (3) H-cholesterol faecal excretion by 39%. Administration of (14) C-cholesterol labelled olive oil orally showed a significant reduction of (14) C-tracer plasma appearance over time with sitagliptin, indicating that this drug promotes RCT through reduced intestinal cholesterol absorption.

High-fat and fructose intake induces insulin resistance, dyslipidemia, and liver steatosis and alters in vivo macrophage-to-feces reverse cholesterol transport in hamsters

Reverse cholesterol transport (RCT) promotes the egress of cholesterol from peripheral tissues to the liver for biliary and fecal excretion. Although not demonstrated in vivo, RCT is thought to be impaired in patients with metabolic syndrome, in which liver steatosis prevalence is relatively high. Golden Syrian hamsters were fed a nonpurified (CON) diet and normal drinking water or a high-fat (HF) diet containing 27% fat, 0.5% cholesterol, and 0.25% deoxycholate as well as 10% fructose in drinking water for 4 wk. Compared to CON, the HF diet induced insulin resistance and dyslipidemia, with significantly higher plasma non-HDL-cholesterol concentrations and cholesteryl ester transfer protein activity. The HF diet induced severe liver steatosis, with significantly higher cholesterol and TG levels compared to CON. In vivo RCT was assessed by i.p. injecting ³H-cholesterol labeled macrophages. Compared to CON, HF hamsters had significantly greater ³H-tracer recoveries in plasma, but not HDL. After 72 h, ³H-tracer recovery in HF hamsters was 318% higher in liver and 75% lower in bile (P < 0.01), indicating that the HF diet impaired hepatic cholesterol fluxes. However, macrophage-derived cholesterol fecal excretion was 45% higher in HF hamsters than in CON hamsters. This effect was not related to intestinal cholesterol absorption, which was 89% higher in HF hamsters (P < 0.05), suggesting a possible upregulation of transintestinal cholesterol excretion. Our data indicate a significant increase in macrophage-derived cholesterol fecal excretion in a hamster model of metabolic syndrome, which may not compensate for the diet-induced dyslipidemia and liver steatosis.

CETP inhibitor torcetrapib promotes reverse cholesterol transport in obese insulin-resistant CETP-ApoB100 transgenic mice

Insulin resistance and type 2 diabetes are associated with low HDL-cholesterol (HDL-c) levels, which would impair reverse cholesterol transport (RCT). A promising therapeutic strategy is to raise HDL with cholesteryl ester transfer protein (CETP) inhibitors, but their effects on RCT remains to be demonstrated in vivo. We therefore evaluated the effects of CETP inhibitor torcetrapib in CETP-apolipoprotein (apo)B100 mice made obese and insulin resistant with a 60% high-fat diet. High-fat diet over 3 months increased body weight and homeostasis model of insulin resistance index by 30% and 846%, respectively (p < 0.01 for both vs. chow-fed mice). Total cholesterol (TC) increased by 46% and HDL-c/TC ratio decreased by 28% (both p < 0.05). Compared to vehicle, high-fat-fed mice treated with torcetrapib (30 mg/kg/day, 3 weeks) showed increased HDL-c levels and HDL-c/TC ratio by 41% and 37% (both p < 0.05). Torcetrapib increased in vitro macrophage cholesterol efflux by 22% and in vivo RCT through a 118% increase in (3) H-bile acids fecal excretion after (3) H-cholesterol labeled macrophage injection (p < 0.01 for both). Fecal total bile acids mass was also increased by 158% (p < 0.001). In conclusion, CETP inhibition by torcetrapib improves RCT in CETP-apoB100 mice. These results emphasize the potential of CETP inhibition to prevent cardiovascular diseases.

Anacetrapib promotes reverse cholesterol transport and bulk cholesterol excretion in Syrian golden hamsters

Cholesteryl ester transfer protein (CETP) transfers cholesteryl ester (CE) and triglyceride between HDL and apoB-containing lipoproteins. Anacetrapib (ANA), a reversible inhibitor of CETP, raises HDL cholesterol (HDL-C) and lowers LDL cholesterol in dyslipidemic patients; however, the effects of ANA on cholesterol/lipoprotein metabolism in a dyslipidemic hamster model have not been demonstrated. To test whether ANA (60 mg/kg/day, 2 weeks) promoted reverse cholesterol transport (RCT), ³H-cholesterol-loaded macrophages were injected and (3)H-tracer levels were measured in HDL, liver, and feces. Compared to controls, ANA inhibited CETP (94%) and increased HDL-C (47%). ³H-tracer in HDL increased by 69% in hamsters treated with ANA, suggesting increased cholesterol efflux from macrophages to HDL. ³H-tracer in fecal cholesterol and bile acids increased by 90% and 57%, respectively, indicating increased macrophage-to-feces RCT. Mass spectrometry analysis of HDL from ANA-treated hamsters revealed an increase in free unlabeled cholesterol and CE. Furthermore, bulk cholesterol and cholic acid were increased in feces from ANA-treated hamsters. Using two independent approaches to assess cholesterol metabolism, the current study demonstrates that CETP inhibition with ANA promotes macrophage-to-feces RCT and results in increased fecal cholesterol/bile acid excretion, further supporting its development as a novel lipid therapy for the treatment of dyslipidemia and atherosclerotic vascular disease.

Diet-induced dyslipidemia impairs reverse cholesterol transport in hamsters

BACKGROUND

Reverse cholesterol transport (RCT) is an anti-atherogenic process by which cholesterol is effluxed from peripheral tissues by high-density lipoprotein (HDL) and returned to the liver for excretion into the bile and faeces. Dyslipidemia is thought to impair RCT through higher triglyceride-rich lipoprotein (TRL), low HDL-cholesterol and higher activity of cholesteryl ester transfer protein (CETP), which transfers cholesteryl esters from HDL to TRL for further hepatic uptake. As CETP pathway would represent a major route in human RCT, we therefore investigated whether diet-induced dyslipidemia impairs RCT in hamster, a CETP-expressing species.

MATERIALS AND METHODS

Golden Syrian hamsters were fed a chow or chow+0·3% cholesterol diet over 4 weeks. Biochemical parameters and in vivo VLDL-triglycerides secretion (Triton WR-1339 injection) were then measured. In vitro macrophage cholesterol efflux was measured, and in vivo macrophage-to-faeces RCT was also assessed after an intraperitoneal injection of (3) H-cholesterol-labelled hamster primary macrophages.

RESULTS

Cholesterol-enriched diet increased plasma total cholesterol (144%), triglycerides (101%), VLDL-triglycerides secretion (175%), CETP activity (44%) and reduced HDL-cholesterol/total cholesterol ratio by 20% (P < 0·01 vs. chow). Cholesterol-enriched diet significantly increased hepatic total cholesterol and triglycerides by 459 and 118% and increased aortic total cholesterol content by 304%. In vitro cholesterol efflux from macrophages to plasma was significantly reduced by 25% with plasma from cholesterol-fed hamsters. In vivo RCT experiments showed a significant 75% reduction of macrophage-derived cholesterol faecal excretion in cholesterol-fed hamsters.

CONCLUSIONS

Overall, these data demonstrate that diet-induced dyslipidemia severely impairs in vivo RCT in hamsters.

Biliary sterol secretion is required for functional in vivo reverse cholesterol transport in mice

BACKGROUND & AIMS

High-density lipoproteins (HDLs) protect against atherosclerotic cardiovascular disease, mainly by promoting reverse cholesterol transport (RCT). Biliary sterol secretion supposedly represents the final step in RCT, but the relevance of this pathway has not been explored. We tested the dependency of RCT on functional biliary sterol secretion.

METHODS

Macrophage-to-feces RCT was studied in mice with abolished (bile duct ligation) or decreased biliary sterol secretion (adenosine triphosphate binding cassette transporter B4 (Abcb4)-/- mice, with and without administration of a liver X receptor [LXR] agonist) after intraperitoneal injection of (3)H-cholesterol-loaded primary macrophage foam cells from mice. Fecal tracer excretion and also fecal mass sterol excretion were measured. Metabolism and tissue uptake of HDL cholesteryl ester was assessed with HDL kinetic studies.

RESULTS

Bile-duct ligation completely abolished RCT from (3)H-cholesterol-loaded macrophages to feces (P < .001). In Abcb4-/- mice lacking biliary cholesterol secretion, RCT was decreased markedly; fecal (3)H-tracer excretion was almost absent within neutral sterols (P < .001) and reduced within bile acids (P < .05). LXR activation stimulated RCT in wild-type (5.5-fold; P < .001) but not Abcb4-/- mice, whereas mass fecal sterol excretion increased similarly in both models (P < .05). Kinetic studies revealed minimal uptake of HDL cholesteryl ester by the intestine, which decreased on LXR activation (P < .05).

CONCLUSIONS

Functional RCT depends on biliary sterol secretion; there is no compensatory increase in RCT via bile acids. The stimulating effect of LXR agonists on RCT requires biliary cholesterol secretion. These results have implications for therapies against atherosclerotic cardiovascular disease targeting the RCT pathway.

P2Y13 receptor is critical for reverse cholesterol transport

A major atheroprotective functionality of high-density lipoproteins (HDLs) is to promote "reverse cholesterol transport" (RCT). In this process, HDLs mediate the efflux and transport of cholesterol from peripheral cells and its subsequent transport to the liver for further metabolism and biliary excretion. We have previously demonstrated in cultured hepatocytes that P2Y(13) (purinergic receptor P2Y, G protein-coupled, 13) activation is essential for HDL uptake but the potential of P2Y(13) as a target to promote RCT has not been documented. Here, we show that P2Y(13)-deficient mice exhibited a decrease in hepatic HDL cholesterol uptake, hepatic cholesterol content, and biliary cholesterol output, although their plasma HDL and other lipid levels were normal. These changes translated into a substantial decrease in the rate of macrophage-to-feces RCT. Therefore, hallmark features of RCT are impaired in P2Y(13)-deficient mice. Furthermore, cangrelor, a partial agonist of P2Y(13), stimulated hepatic HDL uptake and biliary lipid secretions in normal mice and in mice with a targeted deletion of scavenger receptor class B type I (SR-BI) in liver (hypomSR-BI-knockout(liver)) but had no effect in P2Y(13) knockout mice, which indicate that P2Y(13)-mediated HDL uptake pathway is independent of SR-BI-mediated HDL selective cholesteryl ester uptake.

CONCLUSION

These results establish P2Y(13) as an attractive novel target for modulating RCT and support the emerging view that steady-state plasma HDL levels do not necessarily reflect the capacity of HDL to promote RCT.

Both the peroxisome proliferator-activated receptor delta agonist, GW0742, and ezetimibe promote reverse cholesterol transport in mice by reducing intestinal reabsorption of HDL-derived cholesterol

Peroxisome proliferator-activated receptor delta (PPARdelta) agonism increases HDL cholesterol and has therefore the potential to stimulate macrophage-to-feces reverse cholesterol transport (RCT). To test whether PPARdelta activation promotes RCT in mice, in vivo macrophage RCT was assessed using cholesterol-loaded/3H-cholesterol-labeled macrophages injected intraperitoneally. PPARdelta agonist GW0742 (10 mg/kg per day) did not change 3H-tracer plasma appearance, but increased fecal 3H-free sterols excretion by 103% ( p < 0.005) over 48 hours. Total free cholesterol efflux from macrophages to serum (collected from both control and GW0742 groups) was not different, although ABCA1-mediated efflux was significantly higher with GW0742. The metabolic fate of HDL labeled with 3H- cholesteryl ether or 3H-cholesteryl oleate was also measured. While 3H-cholesteryl ether tissue uptake was unchanged, the 3H-tracer recovered in fecal free sterol fraction after 3H-cholesteryl oleate injection increased by 88% with GW0742 ( p < 0.0005). This was associated with a lower Niemann-Pick C1 like 1 (NPC1L1) mRNA expression in the small intestine ( p < 0.05). The same experiments in mice treated with ezetimibe, which blocks NPC1L1, showed a similar 2-fold increase in fecal free sterol excretion after labeled macrophages orHDL injection. In conclusion, PPARdelta activation enhances excretion of macrophage or HDL-derived cholesterol in feces through reduced NPC1L1 expression in mice, comparable to the effect of ezetimibe.

The use of dyslipidemic hamsters to evaluate drug-induced alterations in reverse cholesterol transport

Reverse cholesterol transport (RCT) is the process by which cholesterol is effluxed from peripheral tissues by HDL and returned to the liver for excretion into bile and, ultimately, into feces. Promoting cholesterol efflux from vessel wall macrophages is thought to protect against atherosclerosis and, therefore, RCT represents an attractive therapeutic target for cardiovascular diseases. Although most studies of RCT are conducted in mice, this species does not express cholesteryl ester transfer protein (CETP), which transfers cholesteryl ester from HDL to VLDL/LDL for further uptake by the liver. Given this pathway is the major route of RCT in humans, a CETP-expressing species, such as hamsters, represents a convenient preclinical model for investigating novel therapies for the treatment of dyslipidemia in humans.

Tissue-specific liver X receptor activation promotes macrophage reverse cholesterol transport in vivo

OBJECTIVE

We previously reported that a systemic liver X receptor (LXR) agonist promoted macrophage reverse-cholesterol transport (mRCT) in vivo. Because LXR are expressed in multiple tissues involved in RCT (macrophages, liver, intestine), we analyzed the effect of tissue-specific LXR agonism on mRCT.

METHODS AND RESULTS

In initial studies, the systemic LXR agonist GW3965 failed to promote mRCT in a setting in which LXR was expressed in macrophages but not in liver or intestine. To evaluate the effect of LXR activation specifically in small intestine on mRCT, wild-type mice were treated with either intestinal-specific LXR agonist (GW6340) or systemic LXR agonist (GW3965). Both GW3965 and GW6340 significantly promoted excretion of [(3)H]-sterol in feces by 162% and 52%, respectively. To evaluate the requirement for macrophage LXR activation, we assessed the ability of GW3965 to promote mRCT in wild-type mice using primary macrophages deficient in LXR alpha/beta vs wild-type macrophages. Whereas GW3965 treatment promoted fecal excretion compared with vehicle, its overall ability to promote mRCT was significantly attenuated using LXR alpha/beta knockout macrophages.

CONCLUSIONS

We demonstrate that intestinal-specific LXR agonism promotes macrophage RCT in vivo and that macrophage LXR itself plays an important, but not predominant, role in promoting RCT in response to an LXR agonist.

Liver X receptor activation promotes macrophage-to-feces reverse cholesterol transport in a dyslipidemic hamster model

Liver X receptor (LXR) activation promotes reverse cholesterol transport (RCT) in rodents but has major side effects (increased triglycerides and LDL-cholesterol levels) in species expressing cholesteryl ester transfer protein (CETP). In the face of dyslipidemia, it remains unclear whether LXR activation stimulates RCT in CETP species. We therefore used a hamster model made dyslipidemic with a 0.3% cholesterol diet and treated with vehicle or LXR agonist GW3965 (30 mg/kg bid) over 10 days. To investigate RCT, radiolabeled (3)H-cholesterol macrophages or (3)H-cholesteryl oleate-HDL were then injected to measure plasma and feces radioactivity over 72 or 48 h, respectively. The cholesterol-enriched diet increased VLDL-triglycerides and total cholesterol levels in all lipoprotein fractions and strongly increased liver lipids. Overall, GW3965 failed to improve both dyslipidemia and liver steatosis. However, after (3)H-cholesterol labeled macrophage injection, GW3965 treatment significantly increased the (3)H-tracer appearance by 30% in plasma over 72 h, while fecal (3)H-cholesterol excretion increased by 156% (P < 0.001). After (3)H-cholesteryl oleate-HDL injection, GW3965 increased HDL-derived cholesterol fecal excretion by 64% (P < 0.01 vs. vehicle), while plasma fractional catabolic rate remained unchanged. Despite no beneficial effect on dyslipidemia, LXR activation promotes macrophage-to-feces RCT in dyslipidemic hamsters. These results emphasize the use of species with a more human-like lipoprotein metabolism for drug profiling.

The hyperenergetic-fed obese dog, a model of disturbance of apolipoprotein B-100 metabolism associated with insulin resistance: kinetic study using stable isotopes

The hyperenergetic-fed beagle dog model of obesity-associated insulin resistance has previously demonstrated lipoprotein abnormalities similar to those of obese insulin-resistant humans. The aim of this study was to check, in the insulin-resistant dog, the mechanism leading to abnormalities in the mass of apolipoprotein B-100 (apo B-100) containing lipoproteins. Six healthy male beagle dogs were overfed with a high-fat diet for 28 +/- 2.5 weeks. Obesity was associated with insulin resistance as assessed by the euglycemic hyperinsulinemic clamp technique. The kinetics of very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) apo B-100 were recorded in dogs, at healthy and insulin-resistant states, using a primed constant infusion of [5,5,5-D(3)]leucine. Isotopic enrichment was measured by gas chromatography-mass spectrometry (GC-MS). A multicompartmental model was used for the analysis of tracer kinetics data. Apolipoprotein B-100 concentration was higher in VLDL (2.8-fold, P < .05) but lower in LDL (2-fold, P < .05) in the insulin-resistant compared to the healthy state. Kinetic analysis showed a higher VLDL apo B-100 production (1.7-fold, P < .05). The fractional catabolic rate of VLDL did not change significantly, but the lipolysis was decreased significantly (3-fold, P < .05). The lower LDL apo B-100 level in insulin-resistant dogs was explained by a higher LDL fractional catabolic rate (2.5-fold, P < .05). The mechanisms leading to hypertriglyceridemia (higher production rate and lower lipolysis of VLDL) in insulin-resistant dogs were similar to those described in the insulin-resistant humans.

Metabolism of high density lipoprotein apolipoprotein A-I and cholesteryl ester in insulin resistant dog: a stable isotope study

AIMS

In reverse cholesterol transport (RCT), hepatic Scavenger Receptor class B type I (SR-BI) plays an important role by mediating the selective uptake of high-density lipoprotein cholesteryl ester (HDL-CE). However, little is known about this antiatherogenic mechanism in insulin resistance. HDL-CE selective uptake represents the main process for HDL-CE turnover in dog, a species lacking cholesteryl ester transfer protein activity. We therefore investigate the effects of diet induced insulin resistance on RCT.

METHODS

Five beagle dogs, in healthy and insulin resistant states, underwent a primed constant infusion of [1,2(13)C(2)]acetate and [5,5,5-(2)H(3)]leucine, as labelled precursors of CE and apolipoprotein (apo) A-I, respectively. Data were analysed using modelling methods.

RESULTS

HDL-apo A-I concentration did not change in insulin resistant state but apo A-I absolute production rate (APR) and fractional catabolic rate (FCR) were both higher (2.2- and 2.4-fold, respectively, p < 0.05). HDL-CE levels were lower (1.2-fold, p < 0.05). HDL-CE APR and FCR were both lower (2.3- and 2-fold, respectively, p < 0.05), as well as selective uptake (2.6-fold, p < 0.05).

CONCLUSIONS

Lower HDL-CE selective uptake suggests that RCT is impaired in obese insulin resistant dog.

Low molecular weight heparin self-injection training: assessment of feasibility, tolerance and economic analysis in emergency departments

BACKGROUND

The purpose of this study was to assess low molecular weight heparin auto-injection skills of self-supporting patients, taught by a nurse through a rapid demonstration in an emergency department.

METHODS

The study was a prospective, multicentre study, carried out in emergency departments. It included all ambulatory attending patients over 18 years of age, who were given a lower limb cast in an emergency ward and provided with limited orthopaedic treatment. Eligible patients who accepted self-injection training were given a quick demonstration by the nurse in the emergency ward. A questionnaire about the perception of the patient was completed at the beginning of the treatment and at the end of the treatment. A surveillance chart for recording injections and side effects was also given to the patient, and platelet counts were performed twice weekly.

FINDINGS

Two hundred and fourteen patients have been assessed. Forty-four patients (20.5%) were judged inappropriate for training (n=19) or refused it (n=25). Primary perception of the self-injection method showed absence of fear of injections among patients in 43.7% of cases. Training was successful in 88% of cases. Twenty-one patients out of 170 (12%) gave up after completing the training. Questionnaires given at the end of the treatment found a generally favourable opinion on self-injections among 73.26% of patients (n=86). Compliance was good - 95.5% of patients completed all their injections. Platelet counts were considered appropriate only in 52.5% of cases.

INTERPRETATION

It seems possible to extend the practice of self-injection to other types of injections prescribed after discharge from the emergency department, such as preventive low molecular weight heparin for surgical or medical purposes and curative ambulatory low molecular weight heparin treatment for deep vein thrombosis.

Effects of atorvastatin on high-density lipoprotein apolipoprotein A-I metabolism in dogs

BACKGROUND

The mechanisms involved in the decline of high-density lipoprotein (HDL) levels at a higher dose of atorvastatin have not yet been elucidated. We investigated the effects of atorvastatin on HDL-apolipoprotein (apo) A-I metabolism in dogs, a species lacking cholesteryl ester transfer protein activity.

MATERIALS AND METHODS

Seven ovariectomized normolipidaemic female Beagle dogs underwent a primed constant infusion of [5,5,5-(2)H(3)] leucine to determine HDL-apo A-I kinetics before and after atorvastatin treatment (5 mg kg(-1) d(-1) for 6 weeks). Plasma lipoprotein profiles, activity of HDL-modifying enzymes involved in reverse cholesterol transport and hepatic scavenger receptor class B type I (SR-BI) expression were also studied.

RESULTS

Atorvastatin treatment decreased HDL-cholesterol levels (3.56 +/- 0.24 vs. 2.64 +/- 0.15 mmol L(-1), P < 0.05). HDL-triglycerides were not affected. HDL-phospholipids levels were decreased (4.28 +/- 0.13 vs. 3.29 +/- 0.13 mmol L(-1), P < 0.05), as well as phospholipids transfer protein (PLTP) activity (0.83 +/- 0.05 vs. 0.60 +/- 0.05 pmol microL(-1) min(-1), P < 0.05). Activity of lecithin: cholesterol acyl transferase (LCAT), hepatic lipase (HL) and SR-BI expression did not change. HDL-apo A-I absolute production rate (APR) was higher after treatment (twofold, P < 0.05) as well as fractional catabolic rate (FCR) (threefold, P < 0.05). This resulted in lower HDL-apo A-I levels (2.36 +/- 0.03 vs. 1.55 +/- 0.04 g l(-1), P < 0.05). Plasma lipoprotein profiles showed a decrease in large HDL(1) levels, with lower apo A-I and higher apo E levels in this subfraction.

CONCLUSIONS

Although a high dose of atorvastatin up-regulated HDL-apo A-I production, this drug also increased HDL-apo A-I FCR in dogs. This effect could be explained by a higher uptake of apo E-enriched HDL(1) by hepatic lipoprotein receptors.

Metabolism of cholesterol ester of apolipoprotein B100-containing lipoproteins in dogs: evidence for disregarding cholesterol ester transfer

BACKGROUND

It has been shown that dogs exhibit no cholesterol ester transfer protein (CETP) activity in vitro, in contrast to humans. The aim of our study was to determine modalities of in vivo plasma cholesterol ester turnover in this species, using a kinetic approach with stable isotopes.

MATERIALS AND METHODS

Kinetics of very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) were studied in seven adult male Beagle dogs using a dual isotope approach through endogenous labelling of both their cholesterol moiety and their protein moiety. A primed constant infusion of both [1,2(13)C]acetate and [5,5,5-2H3]leucine enabled us to obtain measurable deuterium enrichments by gas chromatography-mass spectrometry for plasma leucine and apoB100, as well as measurable 13C enrichment by gas chromatography-combustion-isotopic ratio mass spectrometry for unesterified cholesterol and cholesterol ester in the VLDL and LDL. Two identical multicompartmental models (SAAM II) were used together for the analysis of tracer kinetics' data of proteins and cholesterol.

RESULTS

Characterization of the apoB100-containing lipoprotein cholesterol ester model allowed determination of kinetic parameters of VLDL and LDL cholesterol ester metabolism. We succeeded in modelling VLDL and LDL cholesterol ester metabolism and apoB100 metabolism simultaneously. Fractional catabolic rate (FCR) of apoB100 and CE had the same values. Introducing cholesterol ester transfer between lipoproteins in the model did not significantly improve the fit. Total VLDL FCR was 2.97 +/- 01.47 h(-1). Approximately one-quarter corresponded to the direct removal of VLDL (0.81 +/- 00.34 h(-1)) and the remaining three-quarters corresponded to the fraction of VLDL converted to LDL, which represented a conversion of VLDL into LDL of 2.16 +/- 01.16 h(-1). Low-density lipoproteins were produced exclusively from VLDL conversion and were then removed (0.031 +/- 0.004 h(-1)) from plasma.

CONCLUSION

These kinetic data showed that VLDL cholesterol ester and LDL cholesterol ester metabolism followed VLDL and LDL apoB100 metabolism, and that consequently there is no in vivo transfer of cholesterol ester in dogs.

Selective uptake of high density lipoproteins cholesteryl ester in the dog, a species lacking in cholesteryl ester transfer protein activity

Amongst the processes involved in the reverse cholesterol transport (RCT) from organs to liver, including high density lipoproteins-apolipoprotein AI (HDL-apoAI) dependent tissue uptake and cholesteryl ester transfer protein (CETP)-mediated transfers, the selective uptake of cholesteryl ester (CE) is of increasing interest through its antiatherogenic role. The purpose of this report is to develop a simple protocol allowing study of this process in an animal model with easier quantification of CE selective uptake. The dog was chosen essentially because this animal has a low CETP activity and an appropriate size to conduce a kinetic study. Tracer kinetics were performed to estimate in vivo the contributions of the pathways involved in HDL-CE turnover in dogs. Stable isotopes, 13C-acetate and D3-leucine as labeled precursors of CE and apoAI, were infused to fasting dogs. Isotopic enrichments were monitored in plasma unesterified cholesterol and in HDL-CE and apoAI by mass spectrometry. Kinetics were analyzed using compartmental modeling. Results concerned the measurement of the activity of cholesterol esterification (0.13+/-0.032 h(-1)), rate of HDL-apoAI catabolism (0.024+/-0.012 h(-1)), HDL-CE turnover (0.062+/-0.010 h(-1)) and CE selective uptake (0.038+/-0.014 h(-1)). Our results show that CE in dogs is mainly eliminated by selective uptake of HDL-CE (60% of HDL-CE turnover), unlike in other species studied by similar methods in our laboratory. This study shows that among species used to analyze cholesterol metabolism, the dog appears to be the animal in whom HDL-CE selective uptake represents the largest part of HDL-CE turnover.