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

Maternal fructose intake aggravates the harmful effects of a Western diet in rat male descendants impacting their cholesterol metabolism

Scope: fructose consumption from added sugars correlates with the epidemic rise in MetS and CVD. Maternal fructose intake has been described to program metabolic diseases in progeny. However, consumption of fructose-containing beverages is allowed during gestation. Cholesterol is also a well-known risk factor for CVD. Therefore, it is essential to study Western diets which combine fructose and cholesterol and how maternal fructose can influence the response of progeny to these diets. Methods and results: a high-cholesterol (2%) diet combined with liquid fructose (10%), as a model of an unhealthy Western diet, was administered to descendants from control and fructose-fed mothers. Gene (mRNA and protein) expression and plasma, fecal and tissue parameters of cholesterol metabolism were measured. Interestingly, progeny from fructose-fed dams consumed less liquid fructose and cholesterol-rich chow than males from control mothers. Moreover, descendants of fructose-fed mothers fed a Western diet showed an increased cholesterol elimination through bile and feces than males from control mothers. Despite these mitigating circumstances to develop a proatherogenic profile, the same degree of hypercholesterolemia and severity of steatosis were observed in all descendants fed a Western diet, independently of maternal intake. An increased intestinal absorption of cholesterol, synthesis, esterification, and assembly into lipoprotein found in males from fructose-fed dams consuming a Western diet could be the cause. Moreover, an augmented GLP2 signalling seen in these animals would explain this enhanced lipid absorption. Conclusions: maternal fructose intake, through a fetal programming, makes a Western diet considerably more harmful in their descendants than in the offspring from control mothers.

Remodeling Intestinal Microbiota Alleviates Severe Combined Hyperlipidemia-Induced Nonalcoholic Steatohepatitis and Atherosclerosis in LDLR-/- Hamsters

Combined hyperlipidemia (CHL) manifests as elevated cholesterol and triglycerides, associated with fatty liver and cardiovascular diseases. Emerging evidence underscores the crucial role of the intestinal microbiota in metabolic disorders. However, the potential therapeutic viability of remodeling the intestinal microbiota in CHL remains uncertain. In this study, CHL was induced in low-density lipoprotein receptor-deficient (LDLR-/-) hamsters through an 8-week high-fat and high-cholesterol (HFHC) diet or a 4-month high-cholesterol (HC) diet. Placebo or antibiotics were administered through separate or cohousing approaches. Analysis through 16S rDNA sequencing revealed that intermittent antibiotic treatment and the cohousing approach effectively modulated the gut microbiota community without impacting its overall abundance in LDLR-/- hamsters exhibiting severe CHL. Antibiotic treatment mitigated HFHC diet-induced obesity, hyperglycemia, and hyperlipidemia, enhancing thermogenesis and alleviating nonalcoholic steatohepatitis (NASH), concurrently reducing atherosclerotic lesions in LDLR-/- hamsters. Metabolomic analysis revealed a favorable liver lipid metabolism profile. Increased levels of microbiota-derived metabolites, notably butyrate and glycylglycine, also ameliorated NASH and atherosclerosis in HFHC diet-fed LDLR-/- hamsters. Notably, antibiotics, butyrate, and glycylglycine treatment exhibited protective effects in LDLR-/- hamsters on an HC diet, aligning with outcomes observed in the HFHC diet scenario. Our findings highlight the efficacy of remodeling gut microbiota through antibiotic treatment and cohousing in improving obesity, NASH, and atherosclerosis associated with refractory CHL. Increased levels of beneficial microbiota-derived metabolites suggest a potential avenue for microbiome-mediated therapies in addressing CHL-associated diseases.

Theabrownin as a Potential Prebiotic Compound Regulates Lipid Metabolism via the Gut Microbiota, Microbiota-Derived Metabolites, and Hepatic FoxO/PPAR Signaling Pathways

The dysregulation of lipid metabolism poses a significant health threat, necessitating immediate dietary intervention. Our previous research unveiled the prebiotic-like properties of theabrownin. This study aimed to further investigate the theabrownin-gut microbiota interactions and their downstream effects on lipid metabolism using integrated physiological, genomic, metabolomic, and transcriptomic approaches. The results demonstrated that theabrownin significantly ameliorated dyslipidemia, hepatic steatosis, and systemic inflammation induced by a high-fat/high-cholesterol diet (HFD). Moreover, theabrownin significantly improved HFD-induced gut microbiota dysbiosis and induced significant alterations in microbiota-derived metabolites. Additionally, the detailed interplay between theabrownin and gut microbiota was revealed. Analysis of hepatic transcriptome indicated that FoxO and PPAR signaling pathways played pivotal roles in response to theabrownin-gut microbiota interactions, primarily through upregulating hepatic Foxo1, Prkaa1, Pck1, Cdkn1a, Bcl6, Klf2, Ppara, and Pparg, while downregulating Ccnb1, Ccnb2, Fabp3, and Plin1. These findings underscored the critical role of gut-liver axis in theabrownin-mediated improvements in lipid metabolism disorders and supported the potential of theabrownin as an effective prebiotic compound for targeted regulation of metabolic diseases.

Probiotic yogurt regulates gut microbiota homeostasis and alleviates hepatic steatosis and liver injury induced by high-fat diet in golden hamsters

This study aimed to investigate the beneficial effects of probiotic yogurt on lipid metabolism and gut microbiota in metabolic-related fatty liver disease (MAFLD) golden hamsters fed on a high-fat diet (HFD). The results demonstrated that probiotic yogurt significantly reversed the adverse effects caused by HFD, such as body and liver weight gain, liver steatosis and damage, sterol deposition, and oxidative stress after 8 weeks of intervention. qRT-PCR analysis showed that golden hamsters fed HFD had upregulated genes related to adipogenesis, increased free fatty acid infiltration, and downregulated genes related to lipolysis and very low-density lipoprotein secretion. Probiotic yogurt supplements significantly inhibited HFD-induced changes in the expression of lipid metabolism-related genes. Furthermore, 16S rRNA gene sequencing of the intestinal content microbiota suggested that probiotic yogurt changed the diversity and composition of the gut microbiota in HFD-fed hamsters. Probiotic yogurt decreased the ratio of the phyla Firmicutes/Bacteroidetes, the relative abundance of the LPS-producing genus Desulfovibrio, and bacteria involved in lipid metabolism, whereas it increased the relative abundance of short-chain fatty acids producing bacteria in HFD-fed hamsters. Predictive functional analysis of the microbial community showed that probiotic yogurt-modified genes involved in LPS biosynthesis and lipid metabolism. In summary, these findings support the possibility that probiotic yogurt significantly improves HFD-induced metabolic disorders through modulating intestinal microflora and lipid metabolism and effectively regulating the occurrence and development of MAFLD. Therefore, probiotic yogurt supplementation may serve as an effective nutrition strategy for the treatment of patients with MAFLD clinically.

Intestinal lipid absorption and transport in type 2 diabetes

Postprandial hyperlipidaemia is an important feature of diabetic dyslipidaemia and plays an important role in the development of cardiovascular disease in individuals with type 2 diabetes. Postprandial hyperlipidaemia in type 2 diabetes is secondary to increased chylomicron production by the enterocytes and delayed catabolism of chylomicrons and chylomicron remnants. Insulin and some intestinal hormones (e.g. glucagon-like peptide-1 [GLP-1]) influence intestinal lipid metabolism. In individuals with type 2 diabetes, insulin resistance and possibly reduced GLP-1 secretion are involved in the pathophysiology of postprandial hyperlipidaemia. Several factors are involved in the overproduction of chylomicrons: (1) increased expression of microsomal triglyceride transfer protein, which is a key enzyme in chylomicron synthesis; (2) higher stability and availability of apolipoprotein B-48; and (3) increased de novo lipogenesis. Individuals with type 2 diabetes present with disorders of cholesterol metabolism in the enterocytes with reduced absorption and increased synthesis. The increased production of chylomicrons in type 2 diabetes is also associated with a reduction in their catabolism, mostly because of a reduction in activity of lipoprotein lipase. Modification of the microbiota, which is observed in type 2 diabetes, may also generate disorders of intestinal lipid metabolism, but human data remain limited. Some glucose-lowering treatments significantly influence intestinal lipid absorption and transport. Postprandial hyperlipidaemia is reduced by metformin, pioglitazone, alpha-glucosidase inhibitors, dipeptidyl peptidase 4 inhibitors and GLP-1 agonists. The most pronounced effect is observed with GLP-1 agonists, which reduce chylomicron production significantly in individuals with type 2 diabetes and have a direct effect on the intestine by reducing the expression of genes involved in intestinal lipoprotein metabolism. The effect of sodium-glucose cotransporter 2 inhibitors on intestinal lipid metabolism needs to be clarified.

The synergistic ameliorative activity of peroxisome proliferator-activated receptor-alpha and gamma agonists, fenofibrate and pioglitazone, on hippocampal neurodegeneration in a rat model of insulin resistance

Insulin resistance (IR) is a risk factor for metabolic disorders and neurodegeneration. Peroxisome proliferator-activated receptor (PPAR) agonists have been proven to mitigate the neuronal pathology associated with IR. However, the synergetic efficacy of these agonists is yet to be fully described. Hence, we aimed to investigate the efficacy of PPARα/γ agonists (fenofibrate and pioglitazone) on a high-fat diet (HFD) and streptozotocin (STZ)-induced hippocampal neurodegeneration. Male Wistar rats (200 ± 25 mg/body weight [BW]) were divided into five groups. The experimental groups were fed on an HFD for 12 weeks coupled with 5 days of an STZ injection (30 mg/kg/BW, i.p) to induce IR. Fenofibrate (FEN; 100 mg/kg/BW, orally), pioglitazone (PIO; 20 mg/kg/BW, orally), and their combination were administered for 2 weeks postinduction. Behavioral tests were conducted, and blood was collected to determine insulin sensitivity after treatment. Animals were killed for assessment of oxidative stress, cellular morphology characterization, and astrocytic evaluation. HFD/STZ-induced IR increased malondialdehyde (MDA) levels and decreased glutathione (GSH) levels. Evidence of cellular alterations and overexpression of astrocytic protein was observed in the hippocampus. By contrast, monotherapy of FEN and PIO increased the GSH level (p < 0.05), decreased the MDA level (p < 0.05), and improved cellular morphology and astrocytic expression. Furthermore, the combined treatment led to improved therapeutic activities compared to monotherapies. In conclusion, FEN and PIO exerted a therapeutic synergistic effect on HFD/STZ-induced IR in the hippocampus.

HDL and reverse cholesterol transport in humans and animals: Lessons from pre-clinical models and clinical studies

The ability to accept cholesterol from cells and to promote reverse cholesterol transport (RCT) represents the best characterized antiatherogenic function of HDL. Studies carried out in animal models have unraveled the multiple mechanisms by which these lipoproteins drive cholesterol efflux from macrophages and cholesterol uptake to the liver. Moreover, the influence of HDL composition and the role of lipid transporters have been clarified by using suitable transgenic models or through experimental design employing pharmacological or nutritional interventions. Cholesterol efflux capacity (CEC), an in vitro assay developed to offer a measure of the first step of RCT, has been shown to associate with cardiovascular risk in several human cohorts, supporting the atheroprotective role of RCT in humans as well. However, negative data in other cohorts have raised concerns on the validity of this biomarker. In this review we will present the most relevant data documenting the role of HDL in RCT, as assessed in classical or innovative methodological approaches.

Impact of Dietary Lipids on the Reverse Cholesterol Transport: What We Learned from Animal Studies

Reverse cholesterol transport (RCT) is a physiological mechanism protecting cells from an excessive accumulation of cholesterol. When this process begins in vascular macrophages, it acquires antiatherogenic properties, as has been widely demonstrated in animal models. Dietary lipids, despite representing a fundamental source of energy and exerting multiple biological functions, may induce detrimental effects on cardiovascular health. In the present review we summarize the current knowledge on the mechanisms of action of the most relevant classes of dietary lipids, such as fatty acids, sterols and liposoluble vitamins, with effects on different steps of RCT. We also provide a critical analysis of data obtained from experimental models which can serve as a valuable tool to clarify the effects of dietary lipids on cardiovascular disease.

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.

Temporal Development of Dyslipidemia and Nonalcoholic Fatty Liver Disease (NAFLD) in Syrian Hamsters Fed a High-Fat, High-Fructose, High-Cholesterol Diet

The use of translationally relevant animal models is essential, also within the field of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Compared to frequently used mouse and rat models, the hamster may provide a higher degree of physiological similarity to humans in terms of lipid profile and lipoprotein metabolism. However, the effects in hamsters after long-term exposure to a NASH diet are not known. Male Syrian hamsters were fed either a high-fat, high-fructose, high-cholesterol diet (NASH diet) or control diets for up to 12 months. Plasma parameters were assessed at two weeks, one, four, eight and 12 months and liver histopathology and biochemistry was characterized after four, eight and 12 months on the experimental diets. After two weeks, hamsters on NASH diet had developed marked dyslipidemia, which persisted for the remainder of the study. Hepatic steatosis was present in NASH-fed hamsters after four months, and hepatic stellate cell activation and fibrosis was observed within four to eight months, respectively, in agreement with progression towards NASH. In summary, we demonstrate that hamsters rapidly develop dyslipidemia when fed a high-fat, high-fructose, high-cholesterol diet. Moreover, within four to eight months, the NASH-diet induced hepatic changes with resemblance to human NAFLD.

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.

Nuciferine Prevents Hepatic Steatosis by Regulating Lipid Metabolismin Diabetic Rat Model

Objective

This study investigatesthe nuciferine capacity to regulate the liver’s lipid metabolism regarding steatosis and injury in STZ-induced diabetic rats.

Materials and Methods

The rats were randomly divided into groups control, diabetic and nuciferine 200 mg/kg/ day treatment. After 4 days of STZ injection, the nuciferine group was treated and administered via oral gavages for 4 weeks. At the end of experiment, blood, liver, myocardial and muscular samples were collected.

Results

Nuciferine-treated significantly increased the body weight from 339.4g to 367.8g, but significantly decreased the food and water intake compared with diabetic rats. Also, the nuciferine-treated rats had significantly decreased TC, TG, and FFAs in the liver compared with the diabetic group, especially the serum markers of blood glucose. These were associated with the gene expression related to lipogenesis which was significantly down-regulated; the gene expression involved in lipolysis and fatty acid β-oxidation was significantly up-regulated. Discussion and

Conclusion

The data provide evidence that nuciferine supplementation could protect the liver by regulating lipid metabolism gene expression resulting in decreasing the steatosis and injury in diabetic rat. Thus, nuciferine could be developed as a diabetic adjuvant food additive in future.

Acylated Ghrelin and The Regulation of Lipid Metabolism in The Intestine

Acylated ghrelin (AG) is a gastrointestinal (GI) peptide mainly secreted by the stomach that promotes cytosolic lipid droplets (CLD) hypertrophy in adipose tissues and liver. However, the role of AG in the regulation of lipid metabolism in the intestine remains unexplored. This study aimed at determining whether AG influences CLD production and chylomicron (CM) secretion in the intestine. The effects of AG and oleic acid on CLD accumulation and CM secretion were first investigated in cultured Caco-2/15 enterocytes. Intestinal lipid metabolism was also studied in Syrian Golden Hamsters submitted to conventional (CD) or Western (WD) diets for 8 weeks and continuously administered with AG or physiological saline for the ultimate 2 weeks. In cultured Caco-2/15 enterocytes, CLD accumulation influenced CM secretion while AG reduced fatty acid uptake. In WD hamsters, continuous AG treatment amplified chylomicron output while reducing postprandial CLD accumulation in the intestine. The present study supports the intimate relationship between CLD accumulation and CM secretion in the intestine and it underlines the importance of further characterizing the mechanisms through which AG exerts its effects on lipid metabolism in the intestine.

Simultaneous Determination of Biliary and Intestinal Cholesterol Secretion Reveals That CETP (Cholesteryl Ester Transfer Protein) Alters Elimination Route in Mice

OBJECTIVE

Determine the impact of CETP (cholesteryl ester transfer protein) on the route of cholesterol elimination in mice. Approach and Results: We adapted our protocol for biliary cholesterol secretion with published methods for measuring transintestinal cholesterol elimination. Bile was diverted and biliary lipid secretion maintained by infusion of bile acid. The proximal small bowel was perfused with bile acid micelles. In high-fat, high-cholesterol-fed mice, the presence of a CETP transgene increased biliary cholesterol secretion at the expense of transintestinal cholesterol elimination. The increase in biliary cholesterol secretion was not associated with increases in hepatic SR-BI (scavenger receptor BI) or ABCG5 (ATP-binding cassette G5) ABCG8. The decline in intestinal cholesterol secretion was associated with an increase in intestinal Niemann-Pick disease, type C1, gene-like 1 mRNA. Finally, we followed the delivery of HDL (high-density lipoprotein) or LDL (low-density lipoprotein) cholesteryl esters (CE) from plasma to bile and intestinal perfusates. HDL-CE favored the biliary pathway. Following high-fat feeding, the presence of CETP directed HDL-CE away from the bile and towards the intestine. The presence of CETP increased LDL-CE delivery to bile, whereas the appearance of LDL-CE in intestinal perfusate was near the lower limit of detection.

CONCLUSIONS

Biliary and intestinal cholesterol secretion can be simultaneously measured in mice and used as a model to examine factors that alter cholesterol elimination. Plasma factors, such as CETP, alter the route of cholesterol elimination from the body. Intestinal and biliary cholesterol secretion rates are independent of transhepatic or transintestinal delivery of HDL-CE, whereas LDL-CE was eliminated almost exclusively in the hepatobiliary pathway.

Ablation of gut microbiota alleviates obesity-induced hepatic steatosis and glucose intolerance by modulating bile acid metabolism in hamsters

Since metabolic process differs between humans and mice, studies were performed in hamsters, which are generally considered to be a more appropriate animal model for studies of obesity-related metabolic disorders. The modulation of gut microbiota, bile acids and the farnesoid X receptor (FXR) axis is correlated with obesity-induced insulin resistance and hepatic steatosis in mice. However, the interactions among the gut microbiota, bile acids and FXR in metabolic disorders remained largely unexplored in hamsters. In the current study, hamsters fed a 60% high-fat diet (HFD) were administered vehicle or an antibiotic cocktail by gavage twice a week for four weeks. Antibiotic treatment alleviated HFD-induced glucose intolerance, hepatic steatosis and inflammation accompanied with decreased hepatic lipogenesis and elevated thermogenesis in subcutaneous white adipose tissue (sWAT). In the livers of antibiotic-treated hamsters, cytochrome P450 family 7 subfamily B member 1 (CYP7B1) in the alternative bile acid synthesis pathway was upregulated, contributing to a more hydrophilic bile acid profile with increased tauro-β-muricholic acid (TβMCA). The intestinal FXR signaling was suppressed but remained unchanged in the liver. This study is of potential translational significance in determining the role of gut microbiota-mediated bile acid metabolism in modulating diet-induced glucose intolerance and hepatic steatosis in the hamster.

Evaluation of anti-obesity and lipid-lowering properties of Vaccinium myrtillus leaves powder extract in a hamster model

Background Vaccinium myrtillus leaves are known to be rich in phenols and have been used in traditional medicine as an antidiabetic remedy. This study evaluated the powder extract of V. myrtillus leaves obtained with the use of L-arginine and myo-inositol for anti-obesity and lipid-lowering potential in hamsters. Methods Standard phytochemical methods were used to determine the total phenolic and total flavonoid contents of the extract. The obesity condition was induced in Syrian hamsters by feeding them with highly palatable fat- and sugar-rich diet (40.3 kcal% fat) for 12 weeks. From the 10th week of diet feeding, the obese hamsters were treated with the powder extract of V. myrtillus leaves (15, 25 and 35 mg/kg/day, respectively) and "Styfimol" (6.2 mg/kg/day of hydroxycitric acid) as a positive control drug. At the end of the treatment period, the biochemical parameters as well as visceral fat mass were determined. Results Vaccinium myrtillus leaves powder extract at 25 and 35 mg/kg/day caused a significant reduction in body weight gain and visceral fat mass in obese hamsters. Serum triacylglycerols, free fatty acids, total cholesterol and low-density lipoprotein cholesterol (LDL-C) levels were also significantly lower. Besides, the hamsters treated with powder extract at 25 and 35 mg/kg/day had the closest intact value ratio of high-density lipoprotein cholesterol and LDL-C compared with positive control animals. Conclusions The results showed that V. myrtillus leaves powder extract is a promising therapeutic agent for the treatment of obesity and obesity-induced diseases.

Obeticholic acid raises LDL-cholesterol and reduces HDL-cholesterol in the Diet-Induced NASH (DIN) hamster model

The use of rat and mouse models limits the translation to humans for developing novel drugs targeting nonalcoholic steatohepatitis (NASH). Obeticholic acid (OCA) illustrates this limitation since its dyslipidemic effect in humans cannot be observed in these rodents. Conversely, Golden Syrian hamsters have a lipoprotein metabolism mimicking human dyslipidemia since it does express the cholesteryl ester transfer protein (CETP). We therefore developed a Diet-Induced NASH (DIN) hamster model and evaluated the impact of OCA. Compared with chow fed controls, hamsters fed for 20 weeks with a free-choice (FC) diet, developed obesity, insulin resistance, dyslipidemia and NASH (microvesicular steatosis, inflammation, hepatocyte ballooning and perisinusoidal to bridging fibrosis). After 20 weeks of diet, FC fed hamsters were treated without or with obeticholic acid (15mg/kg/day) for 5 weeks. Although a non-significant trend towards higher dietary caloric intake was observed, OCA significantly lowered body weight after 5 weeks of treatment. OCA significantly increased CETP activity and LDL-C levels by 20% and 27%, and reduced HDL-C levels by 20%. OCA blunted hepatic gene expression of Cyp7a1 and Cyp8b1 and reduced fecal bile acids mass excretion by 64% (P < 0.05). Hamsters treated with OCA showed a trend towards higher scavenger receptor Class B type I (SR-BI) and lower LDL-receptor hepatic protein expression. OCA reduced NAS score for inflammation (P < 0.01) and total NAS score, although not significantly. Compared to mouse and rat models, the DIN hamster replicates benefits and side effects of OCA as observed in humans, and should be useful for evaluating novel drugs targeting NASH.

Deep fried edible oils disturb hepatic redox equilibrium and heightens lipotoxicity and hepatosteatosis in male Wistar rats

Hepatosteatosis is a complex disorder, in which insulin resistance and associated dyslipidemic and inflammatory conditions are fundamental. Dietary habit, especially regular consumption of fat and sugar-rich diet, is an important risk factor. Coconut and mustard oils (CO and MO) are medium-chain saturated and monounsaturated fats that are common dietary ingredients among the Indian populations. Present study analyzed the effect of prolonged consumption of the fresh and thermally oxidized forms of these oils on glucose tolerance and hepatosteatosis in male Wistar rats. Thermally oxidized CO (TCO) and MO (TMO) possessed higher amount of lipid peroxidation products and elevated p-anisidine values than their fresh forms. Dietary administration of TCO and TMO along with fructose altered glucose tolerance and increased hyperglycemia in rats. Dyslipidemia was evident by elevated levels of triglycerides and reduced high density lipoprotein cholesterol (HDLc) levels in fructose and edible oil-fed group ( p < 0.05). Additionally, hepatic antioxidant status was diminished and oxidative stress markers were elevated in TCO- and TMO-fed rats. Substantiating these, hike in liver function marker enzyme activities were also observed in these animals. Supporting this, histological analysis revealed higher incidence of microvesicles and hepatocellular ballooning. Results thus suggest that consumption of thermally oxidized fats may cause hepatic damage.

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.

High-Density Lipoprotein Proteomic Composition, and not Efflux Capacity, Reflects Differential Modulation of Reverse Cholesterol Transport by Saturated and Monounsaturated Fat Diets

BACKGROUND

Acute inflammation impairs reverse cholesterol transport (RCT) and reduces high-density lipoprotein (HDL) function in vivo. This study hypothesized that obesity-induced inflammation impedes RCT and alters HDL composition, and investigated if dietary replacement of saturated (SFA) for monounsaturated (MUFA) fatty acids modulates RCT.

METHODS AND RESULTS

Macrophage-to-feces RCT, HDL efflux capacity, and HDL proteomic profiling was determined in C57BL/6j mice following 24 weeks on SFA- or MUFA-enriched high-fat diets (HFDs) or low-fat diet. The impact of dietary SFA consumption and insulin resistance on HDL efflux function was also assessed in humans. Both HFDs increased plasma (3)H-cholesterol counts during RCT in vivo and ATP-binding cassette, subfamily A, member 1-independent efflux to plasma ex vivo, effects that were attributable to elevated HDL cholesterol. By contrast, ATP-binding cassette, subfamily A, member 1-dependent efflux was reduced after both HFDs, an effect that was also observed with insulin resistance and high SFA consumption in humans. SFA-HFD impaired liver-to-feces RCT, increased hepatic inflammation, and reduced ABC subfamily G member 5/8 and ABC subfamily B member 11 transporter expression in comparison with low-fat diet, whereas liver-to-feces RCT was preserved after MUFA-HFD. HDL particles were enriched with acute-phase proteins (serum amyloid A, haptoglobin, and hemopexin) and depleted of paraoxonase-1 after SFA-HFD in comparison with MUFA-HFD.

CONCLUSIONS

Ex vivo efflux assays validated increased macrophage-to-plasma RCT in vivo after both HFDs but failed to capture differential modulation of hepatic cholesterol trafficking. By contrast, proteomics revealed the association of hepatic-derived inflammatory proteins on HDL after SFA-HFD in comparison with MUFA-HFD, which reflected differential hepatic cholesterol trafficking between groups. Acute-phase protein levels on HDL may serve as novel biomarkers of impaired liver-to-feces RCT in vivo.

Effects of Excess Energy Intake on Glucose and Lipid Metabolism in C57BL/6 Mice

Excess energy intake correlates with the development of metabolic disorders. However, different energy-dense foods have different effects on metabolism. To compare the effects of a high-fat diet, a high-fructose diet and a combination high-fat/high-fructose diet on glucose and lipid metabolism, male C57BL/6 mice were fed with one of four different diets for 3 months: standard chow; standard diet and access to fructose water; a high fat diet; and a high fat diet with fructose water. After 3 months of feeding, the high-fat and the combined high-fat/high-fructose groups showed significantly increased body weights, accompanied by hyperglycemia and insulin resistance; however, the high-fructose group was not different from the control group. All three energy-dense groups showed significantly higher visceral fat weights, total cholesterol concentrations, and low-density lipoprotein cholesterol concentrations compared with the control group. Assays of basal metabolism showed that the respiratory quotient of the high-fat, the high-fructose, and the high-fat/high-fructose groups decreased compared with the control group. The present study confirmed the deleterious effect of high energy diets on body weight and metabolism, but suggested that the energy efficiency of the high-fructose diet was much lower than that of the high-fat diet. In addition, fructose supplementation did not worsen the detrimental effects of high-fat feeding alone on metabolism in C57BL/6 mice.

High-fructose feeding promotes accelerated degradation of hepatic LDL receptor and hypercholesterolemia in hamsters via elevated circulating PCSK9 levels

BACKGROUND

High fructose diet (HFD) induces dyslipidemia and insulin resistance in experimental animals and humans with incomplete mechanistic understanding. By utilizing mice and hamsters as in vivo models, we investigated whether high fructose consumption affects serum PCSK9 and liver LDL receptor (LDLR) protein levels.

RESULTS

Feeding mice with an HFD increased serum cholesterol and reduced serum PCSK9 levels as compared with the mice fed a normal chow diet (NCD). In contrast to the inverse relationship in mice, serum PCSK9 and cholesterol levels were co-elevated in HFD-fed hamsters. Liver tissue analysis revealed that PCSK9 mRNA and protein levels were both reduced in mice and hamsters by HFD feeding, however, liver LDLR protein levels were markedly reduced by HFD in hamsters but not in mice. We further showed that circulating PCSK9 clearance rates were significantly lower in hamsters fed an HFD as compared with the hamsters fed NCD, providing additional evidence for the reduced hepatic LDLR function by HFD consumption. The majority of PCSK9 in hamster serum was detected as a 53 kDa N-terminus cleaved protein. By conducting in vitro studies, we demonstrate that this 53 kDa truncated hamster PCSK9 is functionally active in promoting hepatic LDLR degradation.

CONCLUSION

Our studies for the first time demonstrate that high fructose consumption increases serum PCSK9 concentrations and reduces liver LDLR protein levels in hyperlipidemic hamsters. The positive correlation between circulating cholesterol and PCSK9 and the reduction of liver LDLR protein in HFD-fed hamsters suggest that hamster is a better animal model than mouse to study the modulation of PCSK9/LDLR pathway by atherogenic diets.

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.

Crude extracts from Lycium barbarum suppress SREBP-1c expression and prevent diet-induced fatty liver through AMPK activation

Lycium barbarum polysaccharide (LBP) is well known in traditional Chinese herbal medicine that, has beneficial effects. Previous study reported that LBP reduced blood glucose and serum lipids. However, the underlying LBP-regulating mechanisms remain largely unknown. The main purpose of this study was to investigate whether LBP prevented fatty liver through activation of adenosine monophosphate-activated protein kinase (AMPK) and suppression of sterol regulatory element-binding protein-1c (SREBP-1c). Male C57BL/6J mice were fed a low-fat diet, high-fat diet, or 100 mg/kg LBP-treatment diet for 24 weeks. HepG2 cells were treated with LBP in the presence of palmitic acid. In our study, LBP can improve body compositions and lipid metabolic profiles in high-fat diet-fed mice. Oil Red O staining in vivo and in vitro showed that LBP significantly reduced hepatic intracellular triacylglycerol accumulation. H&E staining also showed that LBP can attenuate liver steatosis. Hepatic genes expression profiles demonstrated that LBP can activate the phosphorylation of AMPK, suppress nuclear expression of SREBP-1c, and decrease protein and mRNA expression of lipogenic genes in vivo or in vitro. Moreover, LBP significantly elevated uncoupling protein-1 (UCP1) and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) expression of brown adipose tissue. In summary, LBP possesses a potential novel treatment in preventing diet-induced fatty liver.

APOE*3Leiden.CETP transgenic mice as model for pharmaceutical treatment of the metabolic syndrome

AIMS

This study aimed to investigate systematically (i) the appropriate dietary conditions to induce the features of the MetS in APOE*3Leiden.humanCholesteryl Ester Transfer Protein (E3L.CETP) mice and (ii) whether the response of this model to different antidiabetic and hypolipidemic drugs is similar as in humans.

METHODS

Male obese, IR and dyslipidemic E3L.CETP mice were treated with antidiabetic drugs rosiglitazone, liraglutide or an experimental 11β-hydroxysteroid-dehydrogenase-1 (HSD-1) inhibitor, or with hypolipidemic drugs atorvastatin, fenofibrate or niacin for 4-6 weeks. The effects on bw, IR and plasma and liver lipids were assessed.

RESULTS

Rosiglitazone, liraglutide and HSD-1 inhibitor significantly decreased glucose and insulin levels or IR. Liraglutide and HSD-1 inhibitor also decreased bw. Atorvastatin, fenofibrate and niacin improved the dyslipidemia and fenofibrate and niacin increased high-density lipoprotein (HDL) cholesterol. In addition, hepatic triglycerides were significantly decreased by treatment with rosiglitazone and liraglutide, while hepatic cholesterol esters were significantly decreased by rosiglitazone and atorvastatin.

CONCLUSIONS

We conclude that the E3L.CETP mouse is a promising novel translational model to investigate the effects of new drugs, alone or in combination, that affect IR, diabetic dyslipidemia and non-alcoholic fatty liver disease (NAFLD).

Dietary approaches to improving atheroprotective HDL functions

High-density lipoproteins (HDL) are known to protect against cardiovascular disease (CVD). In addition to facilitating reverse cholesterol transport to remove excess lipids from the body - including atherosclerotic plaques - HDL exhibits antioxidant, anti-inflammatory, vasodilatory, and antithrombotic activities. Together, these properties contribute to the overall atheroprotective nature of HDL. However, similar to many other physiological pathways, these HDL parameters are known to become dysregulated in conditions of metabolic disease. Further, research suggests these alternative HDL properties may be regulated independently of blood HDL-cholesterol (HDL-C) levels, and must therefore be considered when designing HDL-targeted therapies. To date, a number of dietary strategies have been investigated to assess the effect of dietary components on functional properties of HDL beyond HDL-C. This review will highlight the bioactive nutrients, functional foods, and dietary programs known to modulate HDL function as a means of reducing CVD.

An integrated metabonomic approach to studying metabolic profiles in rat models with insulin resistance induced by high fructose

Insulin resistance (IR) is a common risk factor for the development of metabolic diseases, and has gradually become a hot issue for research. It was reported that excessive feeding with high fructose induced insulin resistance in both humans and rats. The aim of this study was to investigate the progression of IR and identify potential biomarkers in urine, plasma and fecal extracts of high fructose-fed rats using a (1)H NMR-based metabonomics approach. The biochemical analysis was also performed. The levels of pyruvate and lactate in the plasma of the IR model rats were reduced significantly, and the levels of citrate and α-ketoglutaric acid (α-KG) in their urine, and the levels of succinate in their feces also decreased, suggesting perturbation of energy metabolism. Decreased levels of taurine in urine and fecal extracts during the whole experiment, together with increased levels of creatine/creatinine in urine, revealed liver and kidney injuries. Decreased levels of choline-containing metabolites in urine and increased levels of betaine in urine and plasma demonstrated altered transmethylation. Changes in hippurate, acetate, propionate and n-butyrate levels suggested disturbance of the intestinal flora in the IR rats. This study indicated that (1)H NMR-based metabonomics can provide biochemical information on the progression of IR and offers a non-invasive means for the discovery of potential biomarkers.

Comparison of two classifications of metabolic syndrome in the pediatric population and the impact of cholesterol

BACKGROUND

To establish the rate of agreement in predicting metabolic syndrome (MS) in different pediatric classifications using percentiles or fixed cut-offs, as well as exploring the influence of cholesterol.

SUBJECTS AND METHODS

Cross-sectional study in a tertiary care center. Nine hundred and twenty-three obese children and adolescents were evaluated for metabolic characteristics, cholesterol levels, the agreement rate and prevalence of MS across age subgroups with pediatric National Cholesterol Education Program/ Adult Treatment Panel III (NCEP-ATP III) and International Diabetes Federation (IDF) classifications.

RESULTS

The overall prevalence of MS was 36.2% and 56.7% with NCEPATP III and IDF. The overall concordance was fair (k: 0.269), with substantial values observed only in children older than 10 (k: 0.708) and 16 yr (0.694). Concordant subjects for both classifications, ≤6 yr, had higher triglycerides, blood pressure (p<0.05) and lower HDL-cholesterol (p<0.0001), with respect to those found to be discordant. Concordant subjects ranging 6-10 yr had all parameters higher than those discordant for IDF (p<0.01) and insulin resistance (p<0.05) than those discordant for NCEP-ATP III. Concordant subjects ≥10 yr presented more altered parameters than those included only in NCEP-ATP III (p<0.05). Overt glucose alterations were uncommon (7.4%; confidence interval 95% 0.1-14.9%), although glucose was modestly higher in MS subjects (p<0.01). Total and LDL-cholesterol was lower in subjects with MS than in those without (p<0.05), and in concordant rather than discordant subjects (p<0.05).

CONCLUSIONS

Classifications of MS do not identify the same pediatric population. Subjects who satisfied any classification were the most compromised. Lipid alterations were precocious in the youngest. Obese youths with MS presented lower total and LDL-cholesterol.

Nuciferine prevents hepatic steatosis and injury induced by a high-fat diet in hamsters

Background

Nuciferine is a major active aporphine alkaloid from the leaves of N. nucifera Gaertn that possesses anti-hyperlipidemia, anti-hypotensive, anti-arrhythmic, and insulin secretagogue activities. However, it is currently unknown whether nuciferine can benefit hepatic lipid metabolism.

Methodology/Principal Findings

In the current study, male golden hamsters were randomly divided into four groups fed a normal diet, a high-fat diet (HFD), or a HFD supplemented with nuciferine (10 and 15 mg/kg·BW/day). After 8 weeks of intervention, HFD-induced increases in liver and visceral adipose tissue weight, dyslipidemia, liver steatosis, and mild necroinflammation in hamsters were analyzed. Nuciferine supplementation protected against HFD-induced changes, alleviated necroinflammation, and reversed serum markers of metabolic syndrome in hamsters fed a HFD. RT-PCR and western blot analyses revealed that hamsters fed a HFD had up-regulated levels of genes related to lipogenesis, increased free fatty acid infiltration, and down-regulated genes involved in lipolysis and very low density lipoprotein secretion. In addition, gene expression of cytochrome P4502E1 and tumor necrosis factor-α were also increased in the HFD group. Nuciferine supplementation clearly suppressed HFD-induced alterations in the expression of genes involved in lipid metabolism.

Conclusions/Significance

Nuciferine supplementation ameliorated HFD-induced dyslipidemia as well as liver steatosis and injury. The beneficial effects of nuciferine were associated with altered expression of hepatic genes involved in lipid metabolism.

The role of the gut in reverse cholesterol transport--focus on the enterocyte

In the arterial intima, macrophages become cholesterol-enriched foam cells and atherosclerotic lesions are generated. This atherogenic process can be attenuated, prevented, or even reversed by HDL particles capable of initiating a multistep pathway known as the macrophage-specific reverse cholesterol transport. The macrophage-derived cholesterol released to HDL is taken up by the liver, secreted into the bile, and ultimately excreted in the feces. Importantly, the absorptive epithelial cells lining the lumen of the small intestine, the enterocytes, express several membrane-associated proteins which mediate the influx of luminal cholesterol and its subsequent efflux at their apical and basolateral sides. Moreover, generation of intestinal HDL and systemic effects of the gut microbiota recently revealed a direct link between the gut and the cholesterol cargo of peripheral macrophages. This review summarizes experimental evidence establishing that the reverse cholesterol transport pathway which initiates in macrophages is susceptible to modulation in the small intestine. We also describe four paths which govern cholesterol passage across the enterocyte and define a role for the gut in the regulation of reverse cholesterol transport. Understanding the concerted function of these paths may be useful when designing therapeutic strategies aimed at removing cholesterol from the foam cells which occupy atherosclerotic lesions.

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.