Modulators of Protein Kinase C Affect SR-BI-Dependent HDL Lipid Uptake in Transfected HepG2 Cells

Therapeutic Potential of Resveratrol and Atorvastatin Following High-Fat Diet Uptake-Induced Nonalcoholic Fatty Liver Disease by Targeting Genes Involved in Cholesterol Metabolism and miR33

The present study was designed to evaluate the effects of resveratrol, atorvastatin, and a combination of resveratrol and atorvastatin on expression levels of genes involved in the cholesterol metabolic pathway in the fatty liver of C57/BL6 mice. A high-fat diet was used to induce fatty liver in C57/BL6 mice treated with resveratrol, atorvastatin, or a combination of resveratrol and atorvastatin. Pathological and biochemical studies were performed. In addition, hepatic gene expressions of ATP-binding cassette transporter A1 (ABCA1), ABCG1, liver X receptor (LXR)α, scavenger receptor B1 (SR-B1), low-density lipoprotein receptor (LDLR), and miR33 were evaluated by the real-time PCR method, and the Western blot method was used to measure the ABCA1, ABCG1, and LXRα protein levels. Resveratrol and atorvastatin reduced fat accumulation in the liver of mice with fatty liver, and this effect was correlated with decreased blood glucose levels, triglyceride, cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol blood levels compared with the positive control (PC) group. In contrast to the animals of the PC group, fatty liver groups that received resveratrol and atorvastatin had a significant effect on the mRNA levels of the ABCA1, ABCG1, LXRα, SR-B1, LDLR, and miR33 genes. Moreover, resveratrol and atorvastatin administration elevated ABCA1 and ABCG1 and reduced LXRα protein expression. Obtained results showed that resveratrol and atorvastatin combination therapy can improve nonalcoholic fatty liver disease by targeting genes involved in cholesterol metabolism and miR33.

Protective properties of sardine and chickpea protein hydrolysates against lipoprotein oxidative damages and some inflammation markers in hypercholesterolemic rats

OBJECTIVE: This study evaluated the effect of sardine (SPH) and chickpea protein hydrolysates (CPH) on oxidant stress and inflammatory profile in cholesterol-fed rats. METHODS: The experiment was undertaken for thirty days on 18 cholesterol-fed Wistar rats (220±10 g) divided into three groups and receiving 1 g/kg of body weight either chickpea protein hydrolysate (CPH), sardine protein hydrolysate (SPH) or casein in water (CG). RESULTS: Compared to CG, SPH and CPH treatment reduced cholesterol, hydroperoxide and malondialdehyde contents in serum, lipoproteins, erythrocytes and aorta. These same treated groups showed also lower serum isoprostane levels. However, serum paraoxonase activity and HDL-antioxidant property were improved only by CPH compared to CG. SOD activity of aorta and erythrocytes was higher in CPH but in SPH group, SOD activity was lower in these tissues and remained unchanged in serum. Furthermore, CPH and SPH stimulated glutathione peroxidase and catalase activities of aorta and erythrocytes. In CPH group, nitric oxide levels of serum, erythrocytes and aorta were increased by respectively 1.4- to 1.8-fold compared to CG and SPH. In addition, among the three groups, CPH exhibited the best anti-inflammatory effect by lowering serum C reactive protein, uric acid and albumin concentrations. CONCLUSIONS: SPH and particularly CPH possess antioxidant and anti-inflammatory properties and could be useful as nutraceuticals for health improving and preventing numerous disorders such as cardiovascular diseases.

PKCβ: Expanding role in hepatic adaptation of cholesterol homeostasis to dietary fat/cholesterol

Cholesterol homeostasis relies on an intricate network of cellular processes whose deregulation in response to Western type high-fat/cholesterol diets can lead to several life-threatening pathologies. Significant advances have been made in resolving the molecular identity and regulatory function of transcription factors sensitive to fat, cholesterol, or bile acids, but whether body senses the presence of both fat and cholesterol simultaneously is not known. Assessing the impact of a high-fat/cholesterol load, rather than an individual component alone, on cholesterol homeostasis is more physiologically relevant because Western diets deliver both fat and cholesterol at the same time. Moreover, dietary fat and dietary cholesterol are reported to act synergistically to impair liver cholesterol homeostasis. A key insight into the role of protein kinase C-β (PKCβ) in hepatic adaptation to high-fat/cholesterol diets was gained recently through the use of knockout mice. The emerging evidence indicates that PKCβ is an important regulator of cholesterol homeostasis that ensures normal adaptation to high-fat/cholesterol intake. Consistent with this function, high-fat/cholesterol diets induce PKCβ expression and signaling in the intestine and liver, while systemic PKCβ deficiency promotes accumulation of cholesterol in the liver and bile. PKCβ disruption results in profound dysregulation of hepatic cholesterol and bile homeostasis and imparts sensitivity to cholesterol gallstone formation. The available results support involvement of a two-pronged mechanism by which intestine and liver PKCβ signaling converge on liver ERK1/2 to dictate diet-induced cholesterol and bile acid homeostasis. Collectively, PKCβ is an integrator of dietary fat/cholesterol signal and mediates changes to cholesterol homeostasis.

Anticipatory role of high density lipoprotein and endothelial dysfunction: an overview

High Density Lipoprotein (HDL) has been witnessed to possess a range of different functions that contribute to its atheroprotective effects. These functions are: the promotion of macrophage cholesterol efflux, reverse cholesterol transport, anti-inflammatory, anti-thrombotic, anti-apoptotic, pro-fibrinolytic and anti-oxidative functions. Paraoxonase 1 (PON1) is an HDL associated enzyme esterase/homocysteinethiolactonase that contributes to the anti-oxidant and anti-atherosclerotic capabilities of HDL. PON1 is directly involved in the etiopathogenesis of atherosclerosis through the modulation of nitric oxide (NO) bioavailability. The aim of this review is to summarize the role of HDL on endothelial homeostasis, and also to describe the recently characterized molecular pathways involved.

High density lipoprotein stimulated migration of macrophages depends on the scavenger receptor class B, type I, PDZK1 and Akt1 and is blocked by sphingosine 1 phosphate receptor antagonists

HDL carries biologically active lipids such as sphingosine-1-phosphate (S1P) and stimulates a variety of cell signaling pathways in diverse cell types, which may contribute to its ability to protect against atherosclerosis. HDL and sphingosine-1-phosphate receptor agonists, FTY720 and SEW2871 triggered macrophage migration. HDL-, but not FTY720-stimulated migration was inhibited by an antibody against the HDL receptor, SR-BI, and an inhibitor of SR-BI mediated lipid transfer. HDL and FTY720-stimulated migration was also inhibited in macrophages lacking either SR-BI or PDZK1, an adaptor protein that binds to SR-BI's C-terminal cytoplasmic tail. Migration in response to HDL and S1P receptor agonists was inhibited by treatment of macrophages with sphingosine-1-phosphate receptor type 1 (S1PR1) antagonists and by pertussis toxin. S1PR1 activates signaling pathways including PI3K-Akt, PKC, p38 MAPK, ERK1/2 and Rho kinases. Using selective inhibitors or macrophages from gene targeted mice, we demonstrated the involvement of each of these pathways in HDL-dependent macrophage migration. These data suggest that HDL stimulates the migration of macrophages in a manner that requires the activities of the HDL receptor SR-BI as well as S1PR1 activity.

Upregulation of caveolin-1 and SR-B1 in mice with non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is one of the most frequent causes of liver diseases, with markedly increased prevalence. However, its mechanisms are not clear. The present study was undertaken to illustrate the role of caveolin-1 (cav1) and the scavenger receptor class B type 1 (SR-B1) in NAFLD.

METHODS

Adult male C57BL/6 mice were fed with a normal diet or high fat and cholesterol (HFC) diet for 14 weeks. The mice were sacrificed to collect plasma and harvest the liver; their plasma lipid concentration was measured. Hepatic cav1 and SR-B1 mRNA and protein expression were determined by real-time quantitative polymerase chain reaction (qPCR) and Western blotting, respectively. In order to study cav1 and SR-B1 distribution and change in hepatocytes, immunohistochemical analysis was performed.

RESULTS

HFC diet increased plasma lipids, induced NAFLD and increased the liver/body weight ratio. Compared to the control mice (n=6), the mRNA and protein levels of cav1 and SR-B1 in liver tissue of the NAFLD mice (n=12) increased significantly (cav1 mRNA: 1.536+/-0.226 vs 0.980+/-0.272, P<0.05; protein: 0.643+/-0.240 vs 0.100+/-0.130, P<0.01; SR-B1 mRNA: 1.377+/-0.125 vs 0.956+/-0.151, P<0.01; protein: 2.156+/-0.507 vs 0.211+/-0.211, P<0.01). Furthermore, both cav1 and SR-B1 immunoreactivity increased and their distribution was also changed, mainly in the plasma membrane of hepatocytes, cytoplasm and membrane of lipid droplets and around.

CONCLUSION

NAFLD is associated with increased concentration of plasma lipids and upregulation of hepatic cav1 and SR-B1 gene and protein expressions, which indicate that cav1 and SR-B1 might play crucial roles in the pathogenesis of NAFLD.

Functionally defective high-density lipoprotein and paraoxonase: a couple for endothelial dysfunction in atherosclerosis

The endothelium is the primary target for biochemical or mechanical injuries caused by the putative risk factors of atherosclerosis. Endothelial dysfunction represents the ultimate link between atherosclerotic risk factors that promote atherosclerosis. HDL-C is thought to exert at least some parts of its antiatherogenic facilities via stimulating endothelial NO production, nearby inhibiting oxidative stress and inflammation. HDL-C is capable of opposing LDL's inductive effects and avoiding the ox-LDL's inhibition of eNOS. Paraoxonase 1 (PON1) is an HDL-associated enzyme esterase which appears to contribute to the antioxidant and antiatherosclerotic capabilities of HDL-C. "Healthy HDL," namely the particle that contains the active Paraoxonase 1, has the power to suppress the formation of oxidized lipids. "Dysfunctional HDL," on the contrary, has reduced Paraoxonase 1 enzyme activity and not only fails in its mission but also potentially leads to greater formation of oxidized lipids/lipoproteins to cause endothelial dysfunction. The association of HDL-C PON1 and endothelial dysfunction depends largely on the molecules with exact damaging effect on NO synthase coupling. Loss of nitric oxide bioavailability has a pivotal role in endothelial dysfunction preceding the appearance of atherosclerosis. Analyses of HDL-C and Paraoxonase1 would be more important in the diagnosis and treatment of atherosclerosis in the very near future.

Alleviative effects of resveratrol on nonalcoholic fatty liver disease are associated with up regulation of hepatic low density lipoprotein receptor and scavenger receptor class B type I gene expressions in rats

Lipid metabolic disorders are widely considered to be one of the most critical and basic link in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). The aim of this study was to illustrate the alleviation function of resveratrol (Res) on NAFLD and the roles of hepatic fatty acid synthase (FAS), low density lipoprotein receptor (LDLr), scavenger receptor class B type I (SR-BI), and thyroid hormone receptor β1 (TRβ1), which are the key molecules involved in lipid metabolism. Adult male Wistar rats were fed a normal diet or high fat/sucrose diet (HFS) with or without resveratrol for 13 weeks. HFS induced NAFLD formation and increased the lipids concentrations in serum and livers of rats, while noticeable improvement has been reached by Res intervention. Moreover, Res protected against HFS-induced decrease in hepatic LDLr and SR-BI mRNA and protein expressions, whereas TRβ1 expressions were impervious with/without Res. Unexpectedly, hepatic FAS gene expressions were markedly diminished in NAFLD rats and were gradually increased by treatment with Res. These data indicate that the alleviative effects of Res on NAFLD are associated with up regulation of hepatic LDLr and SR-BI gene expressions, which provide new insights into the pharmacological targets of Res in the prevention of NAFLD.

Excess iodine and high-fat diet combination modulates lipid profile, thyroid hormone, and hepatic LDLr expression values in mice

The aim of this study was to illustrate the combined effect of excess iodine and high-fat diet on lipid metabolism and its potential molecular mechanism. Sixty Balb/c mice were randomly allocated to three control groups or three excess iodine groups and fed with a high-fat diet in the absence or presence of 1,200 μg/L iodine for 1, 3, or 6 months, respectively. Serum lipid parameters and serum thyroid hormones were measured. Expressions of scavenger receptor class B type-I (SR-BI) and low density lipoproteins receptor (LDLr) mRNA and protein in liver were detected. Thyroid histology and liver type 1 iodothyronine deiodinase activity were analyzed. At the end of 3 and 6 months, compared with control, serum TC, TG, and LDL-C in excess iodine group were significantly lower (p < 0.05). LDLr expression in liver was increased significantly (p < 0.05) and parallel to the change of serum TC and TG. TT3 and TT4 levels in serum were elevated and TSH decreased significantly (p < 0.05). Liver type I iodothyronine deiodinase activity was significantly higher (p < 0.05) than control at the end of 6 months. Moreover, a time course damage effect of excess iodine combined with high-fat diet on thyroid glands was observed. The present findings demonstrated that excess iodine combined with high-fat diet could cause damage to thyroid glands and lead to thyroid hormone disorder. Those in turn caused the upregulation of hepatic LDLr gene, which resulted in the disorder in serum lipids.