ABSTRACT
Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. Fat accumulation "sensitizes" the liver to insult and leads to nonalcoholic steatohepatitis (NASH). G protein-coupled receptor 35 (GPR35) is involved in metabolic stresses, but its role in NAFLD is unknown. We report that hepatocyte GPR35 mitigates NASH by regulating hepatic cholesterol homeostasis. Specifically, we found that GPR35 overexpression in hepatocytes protected against high-fat/cholesterol/fructose (HFCF) diet-induced steatohepatitis, whereas loss of GPR35 had the opposite effect. Administration of the GPR35 agonist kynurenic acid (Kyna) suppressed HFCF diet-induced steatohepatitis in mice. Kyna/GPR35 induced expression of StAR-related lipid transfer protein 4 (STARD4) through the ERK1/2 signaling pathway, ultimately resulting in hepatic cholesterol esterification and bile acid synthesis (BAS). The overexpression of STARD4 increased the expression of the BAS rate-limiting enzymes cytochrome P450 family 7 subfamily A member 1 (CYP7A1) and CYP8B1, promoting the conversion of cholesterol to bile acid. The protective effect induced by GPR35 overexpression in hepatocytes disappeared in hepatocyte STARD4-knockdown mice. STARD4 overexpression in hepatocytes reversed the aggravation of HFCF diet-induced steatohepatitis caused by the loss of GPR35 expression in hepatocytes in mice. Our findings indicate that the GPR35-STARD4 axis is a promising therapeutic target for NAFLD.
ABSTRACT
Parkin, an E3 ubiquitin ligase, plays a role in maintaining mitochondrial homeostasis through targeting damaged mitochondria for mitophagy. Accumulating evidence suggests that the acetylation modification of the key mitophagy machinery influences mitophagy level, but the underlying mechanism is poorly understood. Here, our study demonstrated that inhibition of histone deacetylase (HDAC) by treatment of HDACis activates mitophagy through mediating Parkin acetylation, leading to inhibition of cervical cancer cell proliferation. Bioinformatics analysis shows that Parkin expression is inversely correlated with HDAC2 expression in human cervical cancer, indicating the low acetylation level of Parkin. Using mass spectrometry, Parkin is identified to interact with two upstream molecules, acetylase acetyl-CoA acetyltransferase 1 (ACAT1) and deacetylase HDAC2. Under treatment of suberoylanilide hydroxamic acid (SAHA), Parkin is acetylated at lysine residues 129, 220 and 349, located in different domains of Parkin protein. In in vitro experiments, combined mutation of Parkin largely attenuate the interaction of Parkin with PTEN induced putative kinase 1 (PINK1) and the function of Parkin in mitophagy induction and tumor suppression. In tumor xenografts, the expression of mutant Parkin impairs the tumor suppressive effect of Parkin and decreases the anticancer activity of SAHA. Our results reveal an acetylation-dependent regulatory mechanism governing Parkin in mitophagy and cervical carcinogenesis, which offers a new mitophagy modulation strategy for cancer therapy.
ABSTRACT
AIM To investigate the effects of berberine-evodiamine compatibility on expressions of intestinal acyl-CoA:cholesterol acyltransferase 2 (ACAT2),apolipoprotein B48 (ApoB48),and Niemann-Pick C1 Like 1 (NPC1L1) proteins in hypercholesterolemic rats.METHODS Fifty SD rats were assigned to control and model groups.After establishing the hypercholesterolemic rat model by feeding high fat and high cholesterol food,forty SD rats were equally divided into model control group,atorvastatin group,berberine-evodiamine compatibility groups (89.2 mg/kg,178.4 mg/kg).After four weeks treatment,serum triglycerides (TG),total cholesterol (TC),low-density lipoprotein cholesterol (LDL-C),high density lipoprotein cholesterol (HDL-C) were detected.Then the contents of cholesterol and β-sitoesterol in serum were determined by GC.The expressions of ACAT2,ApoB48 and NPC1 L1 proteins in the small intestine were assayed with immunohistochemistry technology.RESULTS Serum TC,TG and liver TC were significantly decreased in 89.2 mg/kg and 178.4 mg/kg berberineevodiamine compatibility groups compared with those in the model control group (P ＜ 0.01).Serum LDL-C and liver TC were also significantly decreased in 89.2 mg/kg berberine-evodiamine compatibility group (P ＜ 0.05).GC analysis indicated that the amount of cholesterol level and β-sitoesterol in serum were decreased in 178.4 mg/kg berberine-evodiamine compatibility group (P ＜ 0.05) and 89.2 mg/kg berberine-evodiamine compatibility group (P ＜ 0.01).Immunohistochemistry analysis manifested that the average luminous density of ACAT2,ApoB48 and NPC1L1 proteins in two dosages of berberine-evodiamine compatibility group were descended markedly compared with those in the model control group (P ＜ 0.05 or P ＜ 0.01).CONCLUSION The mechanisms underlying the cholesterol metabolism activity of berberine-evodiamine compatibility are mediated most likely by down-regulating the expressions of intestinal ACAT2,ApoB48 and NPC1 L1 proteins in hypercholesterolemic rats.
ABSTRACT
AIM To investigate the effects of berberine-evodiamine compatibility on expressions of intestinal acyl-CoA:cholesterol acyltransferase 2 (ACAT2),apolipoprotein B48 (ApoB48),and Niemann-Pick C1 Like 1 (NPC1L1) proteins in hypercholesterolemic rats.METHODS Fifty SD rats were assigned to control and model groups.After establishing the hypercholesterolemic rat model by feeding high fat and high cholesterol food,forty SD rats were equally divided into model control group,atorvastatin group,berberine-evodiamine compatibility groups (89.2 mg/kg,178.4 mg/kg).After four weeks treatment,serum triglycerides (TG),total cholesterol (TC),low-density lipoprotein cholesterol (LDL-C),high density lipoprotein cholesterol (HDL-C) were detected.Then the contents of cholesterol and β-sitoesterol in serum were determined by GC.The expressions of ACAT2,ApoB48 and NPC1 L1 proteins in the small intestine were assayed with immunohistochemistry technology.RESULTS Serum TC,TG and liver TC were significantly decreased in 89.2 mg/kg and 178.4 mg/kg berberineevodiamine compatibility groups compared with those in the model control group (P ＜ 0.01).Serum LDL-C and liver TC were also significantly decreased in 89.2 mg/kg berberine-evodiamine compatibility group (P ＜ 0.05).GC analysis indicated that the amount of cholesterol level and β-sitoesterol in serum were decreased in 178.4 mg/kg berberine-evodiamine compatibility group (P ＜ 0.05) and 89.2 mg/kg berberine-evodiamine compatibility group (P ＜ 0.01).Immunohistochemistry analysis manifested that the average luminous density of ACAT2,ApoB48 and NPC1L1 proteins in two dosages of berberine-evodiamine compatibility group were descended markedly compared with those in the model control group (P ＜ 0.05 or P ＜ 0.01).CONCLUSION The mechanisms underlying the cholesterol metabolism activity of berberine-evodiamine compatibility are mediated most likely by down-regulating the expressions of intestinal ACAT2,ApoB48 and NPC1 L1 proteins in hypercholesterolemic rats.
ABSTRACT
Several proteins are involved in the absorption of cholesterol in small intestine.Niemann-Pick C1 like 1 (NPC1L1) mainly mediates the absorption of cholesterol, and acyl-coenzyme A ( CoA)∶cholesterol acyltransferase 2 (ACAT2) catalyzes the free cholesterol absorpted by intestine into cholesterol ester,while unesterified free cholesterol is secreted into intestinal lumen by ATP-binding cassette(ABC) transporters G5/G8(ABCG5/ABCG8).Transcription factor liver X receptor( LXR) plays an important role in the process of intestinal cholesterol absorption.The research progress in NPC1L1,ABCG5/ABCG8,ACAT2 and LXR is reviewed in this article.
ABSTRACT
The traditional usage of noni fruit did not include any claims for lowering cholesterol levels in humans. However, recently a commercial noni fruit juice blend, Tahitian Noni Original® Bioactive (TNOB),was shown in a double blind, and placebo control clinical trial to significantly lower cholesterol levels in current smokers. But, its effect on cholesterol levels of nonsmokers with normal cholesterol levels, and its mechanisms of action, has not been fully elucidated. The current study evaluates the effects of various noni preparations (TNOB, NFJC (noni fruit juice concentrates), NFJME (noni fruit juice methanol extract)) on HMG-CoA Reductase and ACAThepatic/intestine enzymes in vitro. Further, TNOB was evaluated for its potential cholesterol-lowering effects in 10 non-smoking subjects with normal to mild cholesterol levels. TNOB and NFJC both inhibited HMG-CoA Reductase, and ACAT enzymes concentration-dependently in-vitro, and NFJC has a <1.0 mg/mL IC50 on HMG-CoA Reductase enzymes. NFJME, the active fraction from the noni fruit juice, in 100μg/mL, inhibited HMG-CoA reductase by 81%. TNOB showed a trend towards lowering total cholesterol and LDL levels while increasing HDL levels in nonsmokers. Noni fruit juice has the potential to lower cholesterol levels in nonsmokers perhaps via its inhibitory effects on HMGCoA reductase and ACAT enzymes as its possible mechanism of action. However, a larger clinical trial is warranted to assess its effects in non-smokers with higher cholesterol levels above 220 mg/dL to evaluate the nature of this cholesterol-lowering trend seen in this pilot study.
ABSTRACT
The aim of the present study was to investigate the hypocholesterolemic effect and potential of tyramine derivatives from Lycii Cortex Radicis (LCR), the root bark of lycium (Lycium chenese Miller) in reducing lipid peroxidation. The activities of enzymes, hepatic 3-hydroxy 3-methylglutaryl (HMG) CoA reductase and acyl-CoA:cholesterol acyltransferase (ACAT) and LDL oxidation were measured in vitro and animal experiments were also performed by feeding LCR extracts to rats. The test compounds employed for in vitro study were trans-N-p-coumaroyltyramine (CT) and trans-N-feruloyltyramine (FT), LCR components, N-(p-coumaroyl)serotonin (CS) and N-feruloylserotonin (FS) from safflower seeds, ferulic acid (FA) and 10-gingerol. It was observed that FT and FS at the concentration of 1.2 mg/mL inhibited liver microsomal HMG CoA reductase activity by ~40%, but no inhibition of activity was seen in the cases of CT, CS, FA and 10-gingerol. Whereas, ACAT activity was inhibited ~50% by FT and CT, 34-43% by FS and CS and ~80% by 10-gingerol at the concentration of 1 mg/mL. A significant delay in LDL oxidation was induced by CT, FT, and 10-gingerol. For the animal experiment, five groups of Sprague-Dawley male rats were fed high fat diets containing no test material (HF-control), 1 and 2% of LCR ethanol extract (LCR1 and LCR2), and 1% of extracts from safflower seed (Saf) and ginger (Gin). The results indicated that total cholesterol level was significantly lower in Saf, LCR2 and Gin groups, and HDL cholesterol level was lower only in Gin group when compared with HF-control group; while there was no difference in the serum triglyceride levels among the five experimental groups. The level of liver cholesterol was significantly lower in LCR1 and LCR2 groups than HF-control. Serum levels of TBARS were significantly lower only in LCR2 group when compared with HF-control group. From the observed results, we concluded that LCR can be utilized as a hypocholesterolemic ingredient in combination with ginger, especially for functional foods.