Ethanol Extract of Pinus koraiensis Leaf Ameliorates Alcoholic Fatty Liver via the Activation of LKB1–AMPK Signaling In Vitro and In Vivo

Although Pinus koraiensis leaf (PKL) was reported for its anti‐diabetes, anti‐obesity and anticancer effects as a folk remedy, the inhibitory effect of PKL on alcoholic fatty liver has never been elucidated yet. This study investigated the molecular mechanisms of PKL on alcoholic fatty liver in HepG2 cells, Sprague Dawley (SD) rats and Imprinting Control Region (ICR) mice. Pinus koraiensis leaf increased phosphorylation of liver kinase B1 (LKB1)/AMP‐activated protein kinase signaling, low‐density lipoprotein receptor and decreased fatty acid biosynthesis‐related proteins such as sterol regulatory element‐binding protein 1c, fatty acid synthase, 3‐hydroxy‐3‐methylglutaryl‐CoA reductase in HepG2 cells. In SD rats with 25% alcohol‐induced fatty liver, PKL suppressed the levels of aspartate aminotransferase and triglyceride and also enhanced the activities of antioxidant enzymes including superoxide dismutase, glutathione peroxidase and glutathione s‐transferase compared with untreated control. Furthermore, PKL increased serum alcohol dehydrogenase and serum aldehyde dehydrogenase, but decreased serum alcohol concentration in ICR mice after alcohol administration. Consistently, histochemical analysis revealed that PKL attenuated alcohol‐induced fatty liver in SD rats. Overall, these findings suggest that PKL ameliorates alcohol‐induced fatty liver via activation of LKB1–AMP‐activated protein kinase and modulation of proteins related to lipogenesis synthesis, cholesterol synthesis and fatty acid oxidation. Copyright © 2017 John Wiley & Sons, Ltd.     

Effects of Sinensetin on Lipid Metabolism in Mature 3T3‐L1 Adipocytes

Sinensetin is a rare polymethoxylated flavone found in certain citrus fruits. In this study, we investigated the effects of sinensetin on lipid metabolism in mature 3T3‐L1 adipocytes. Sinensetin decreased the expression of sterol regulatory element‐binding protein 1c (SREBP1c), suggesting its antiadipogeneic property via downreguation of SREBP1c. Also, sinensetin increased the phosphorylation of protein kinase A and hormone‐sensitive lipase, indicating its lipolytic property via a cAMP‐mediated signaling pathway. Moreover, sinensetin inhibited insulin‐stimulated glucose uptake by decreasing the phosphorylation of insulin receptor substrate and Akt. Furthermore, sinensetin increased the phosphorylation of AMP‐activated protein kinase (AMPK) and acetyl‐CoA carboxylase. It also upregulated mRNA expression of carnitine palmitoyltransferase‐1a, suggesting that sinensetin enhances fatty acid β‐oxidation through the AMPK pathway. Taken together, these results suggest that sinensetin may have potential as a natural agent for prevention/improvement of obesity. Copyright © 2012 John Wiley & Sons, Ltd.     

Hypolipidemic Activity of Okra is Mediated Through Inhibition of Lipogenesis and Upregulation of Cholesterol Degradation

Little is known about the hypolipidemic activity of okra; therefore, we investigated the hypolipidemic activity of okra and its interaction with gene expression of several key components involved in lipid homeostasis. Male C57BL/6 mice were randomly divided into three groups and fed with hyperlipidemic diet or two hyperlipidemic diets supplemented with 1% or 2% okra powder for eight weeks. Results demonstrated that okra dose‐dependently decreased serum and hepatic total cholesterol and triglyceride, and enhanced fecal excretion of bile acids. Gene expression analysis revealed that okra upregulated cholesterol 7α‐hydroxylase (CYP7A1) expression, downregulated expression of sterol regulatory element‐binding protein 1c (SREBP1c) and fatty acid synthase (FAS), with no effect on sterol regulatory element‐binding protein 2 (SREBP2), 3‐hydroxy‐3‐methylglutaryl‐CoA reductase (HMGR), low‐density lipoprotein receptor (LDLR) and carnitine palmitoyltransferase‐1A (CPT1A). It was suggested that hypolipidemic activity of okra was mediated most likely by upregulation of cholesterol degradation through CYP7A1 and by inhibition of lipogenesis through SREBP1c and FAS. Okra raw and fractionated polysaccharide showed strong bile acid binding capacity in vitro, which may contribute to the hypolipidemic activity observed. In conclusion, okra has potential application in the management of hyperlipidemia and its associated metabolic disorders. Copyright © 2013 John Wiley & Sons, Ltd.     

Reactive Oxygen Species‐Mediated Activation of AMP‐Activated Protein Kinase and c‐Jun N‐terminal Kinase Plays a Critical Role in Beta‐Sitosterol‐Induced Apoptosis in Multiple Myeloma U266 cells

Although beta‐sitosterol has been well known to have anti‐tumor activity in liver, lung, colon, stomach, breast and prostate cancers via cell cycle arrest and apoptosis induction, the underlying mechanism of anti‐cancer effect of beta‐sitosterol in multiple myeloma cells was never elucidated until now. Thus, in the present study, the role of reactive oxygen species (ROS) in association with AMP‐activated protein kinase (AMPK) and c‐Jun N‐terminal kinase (JNK) pathways was demonstrated in beta‐sitosterol‐treated multiple myeloma U266 cells. Beta‐sitosterol exerted cytotoxicity, increased sub‐G₁ apoptotic population and activated caspase‐9 and ‐3, cleaved poly (ADP‐ribose) polymerase (PARP) followed by decrease in mitochondrial potential in U266 cells. Beta‐sitosterol promoted ROS production, activated AMPK, acetyl‐CoA carboxylase (ACC) and JNK in U266 cells. Also, beta‐sitosterol attenuated the phosphorylation of AKT, mammalian target of rapamycin and S6K, and the expression of cyclooxygenase‐2 and VEGF in U266 cells. Conversely, AMPK inhibitor compound C and JNK inhibitor SP600125 suppressed apoptosis induced by beta‐sitosterol in U266 cells. Furthermore, ROS scavenger N‐acetyl L‐cysteine attenuated beta‐sitosterol‐mediated sub‐G₁ accumulation, PARP cleavage, JNK and AMPK activation in U266 cells. Overall, these findings for the first time suggest that ROS‐mediated activation of cancer metabolism‐related genes such as AMPK and JNK plays an important role in beta‐sitosterol‐induced apoptosis in U266 multiple myeloma cells. Copyright © 2013 John Wiley & Sons, Ltd.     

Apoptotic effect of lambertianic acid through AMPK/FOXM1 signaling in MDA‐MB231 breast cancer cells

Though lambertianic acid (LA) was known to exert antitumor effect in liver and prostate cancers, its underlying anticancer mechanism is never reported in breast cancers so far. Thus, in this study, apoptotic mechanism of LA was elucidated in MDA‐MB‐231 breast cancer cells. Here, LA increased cytotoxicity in MCF‐7 and MDA‐MB‐231 cells; enhanced sub‐G1 population, G2/M arrest, and cleaved poly(ADP‐ribose) polymerase; activated phosphorylation of AMP‐activated protein kinase (AMPK)/acetyl‐CoA carboxylase pathway; and also suppressed phosphorylation of AKT and the expression of forkhead box M1 (FOXM1), X‐linked inhibitor of apoptosis protein, B‐cell lymphoma 2, and CyclinB1 in MDA‐MB‐231 cells. Furthermore, AMPK inhibitor compound C reversed the effect of LA on FOXM1, Cyclin B1, and cleaved poly(ADP‐ribose) polymerase in MDA‐MB‐231 cells. Notably, immunoprecipitation revealed that LA disturbed the direct binding of AKT and FOXM1 in MDA‐MB‐231 cells. Overall, these findings suggest that LA‐induced apoptosis is mediated via activation of AMPK and inhibition of AKT/FOXM1 signaling pathway.     

Bromophenol (5‐bromo‐3,4‐dihydroxybenzaldehyde) isolated from red alga Polysiphonia morrowii inhibits adipogenesis by regulating expression of adipogenic transcription factors and AMP‐activated protein kinase activation in 3T3‐L1 adipocytes

The aim of the present study was to investigate the effect of 5‐bromo‐3,4‐dihydroxybenzaldehyde (BD) isolated from Polysiphonia morrowii on adipogenesis and differentiation of 3T3‐L1 preadipocytes into mature adipocytes and its possible mechanism of action. Levels of lipid accumulation and triglyceride were significantly lower in BD treated cells than those in untreated cells. In addition, BD treatment reduced protein expression levels of peroxisome proliferator‐activated receptor‐γ, CCAAT/enhancer‐binding proteins α, and sterol regulatory element‐binding protein 1 compared with control (no treatment). It also reduced expression levels of adiponectin, leptin, fatty acid synthase, and fatty acid binding protein 4. AMP‐activated protein kinase activation was found to be one specific mechanism involved in the effect of BD. These results demonstrate that BD possesses inhibitory effect on adipogenesis through activating AMP‐activated protein kinase signal pathway.