Fucoxanthin attenuates fatty acid-induced lipid accumulation in FL83B hepatocytes through regulated Sirt1/AMPK signaling pathway

Licochalcone D ameliorates lipid metabolism in hepatocytes by modulating lipogenesis and autophagy

Metabolic dysfunction-associated fatty liver disease is a metabolic disease caused by abnormal lipid accumulation in the liver. Excessive lipid accumulation results in liver inflammation and fibrosis. Previous studies have demonstrated that the chalcone licochalcone D, which is isolated from Glycyrrhiza inflata Batal, has anti-tumor and anti-inflammatory effects. The present study explored whether licochalcone D can regulate lipid accumulation in fatty liver cells. FL83B hepatocytes were incubated with oleic acid to establish a fatty liver cell model, and then treated with licochalcone D to evaluate the molecular mechanisms underlying the regulation of lipid metabolism. In addition, male C57BL/6 mice were fed a methionine/choline-deficient diet to induce an animal model of metabolic dysfunction-associated steatohepatitis (MASH) and given 5 mg/kg licochalcone D by intraperitoneal injection. In cell experiments, licochalcone D significantly reduced lipid accumulation in fatty liver cells and reduced sterol regulatory element-binding protein 1c expression, blocking fatty acid synthase production. Licochalcone D increased adipose triglyceride lipase and carnitine palmitoyltransferase 1 expression, enhancing lipolysis and fatty acid β-oxidation, respectively. Licochalcone D also significantly increased SIRT-1 and AMPK phosphorylation, reducing acetyl-CoA carboxylase phosphorylation and inhibiting fatty acid synthesis. Licochalcone D also increased the fusion of autophagosomes and lysosomes to promote autophagy, reducing oil droplet accumulation in fatty liver cells. In the animal experiments, licochalcone D effectively reduced the number of lipid vacuoles and degree of fibrosis in liver tissue and inhibited liver inflammation. Thus, licochalcone D can improve MASH by reducing lipid accumulation, inhibiting inflammation, and increasing autophagy.

Fucoxanthin restructures the gut microbiota and metabolic functions of non-obese individuals in an in vitro fermentation model

Fucoxanthin, a carotenoid exclusively derived from algae, exerts its bioactivities with the modulation of the gut microbiota in mice. However, mechanisms through which fucoxanthin regulates the gut microbiota and its derived metabolites/metabolism in humans remain unclear. In this study, we investigated the effects of fucoxanthin on the gut microbiota and metabolism of non-obese individuals using an in vitro simulated digestion-fermentation cascade model. The results showed that about half of the fucoxanthin was not absorbed in the intestine, thus reaching the colon. The gut microbiota from fecal samples underwent significant changes after 48 or 72 hours in vitro fermentation. Specifically, fucoxanthin significantly enhanced the relative abundance of Bacteroidota and Parabacteroides, leading to improved functions of the gut microbiota in its development, glycan biosynthesis and metabolism as well as in improving the digestive system, endocrine system and immune system. The recovery of fucoxanthin during fermentation showed a decreasing trend with the slight bio-conversion of fucoxanthinol. Notably, fucoxanthin supplementation significantly altered metabolites, especially bile acids and indoles in the simulated human gut ecosystem. Correlation analysis indicated the involvement of the gut microbiota in the manipulation of these metabolites by fucoxanthin. Moreover, all these altered metabolites revealed the improvement in the capacity of fucoxanthin in manipulating gut metabolism, especially lipid metabolism. Overall, fucoxanthin determinedly reshaped the gut microbiota and metabolism, implying its potential health benefits in non-obese individuals.

Gypenoside XIII regulates lipid metabolism in HepG2 hepatocytes and ameliorates nonalcoholic steatohepatitis in mice

Gypenoside XIII is isolated from Gynostemma pentaphyllum (Thunb.) Makino. In mice, G. pentaphyllum extract and gypenoside LXXV have been shown to improve non-alcoholic steatohepatitis (NASH). This study investigated whether gypenoside XIII can regulate lipid accumulation in fatty liver cells or attenuate NASH in mice. We used HepG2 hepatocytes to establish a fatty liver cell model using 0.5 mM oleic acid. Fatty liver cells were treated with different concentrations of gypenoside XIII to evaluate the molecular mechanisms of lipid metabolism. In addition, a methionine/choline-deficient diet induced NASH in C57BL/6 mice, which were given 10 mg/kg gypenoside XIII by intraperitoneal injection. In fatty liver cells, gypenoside XIII effectively suppressed lipid accumulation and lipid peroxidation. Furthermore, gypenoside XIII significantly increased SIRT1 and AMPK phosphorylation to decrease acetyl-CoA carboxylase phosphorylation, reducing fatty acid synthesis activity. Gypenoside XIII also decreased lipogenesis by suppressing sterol regulatory element-binding protein 1c and fatty acid synthase production. Gypenoside XIII also increased lipolysis and fatty acid β-oxidation by promoting adipose triglyceride lipase and carnitine palmitoyltransferase 1, respectively. In an animal model of NASH, gypenoside XIII effectively decreased the lipid vacuole size and number and reduced liver fibrosis and inflammation. These findings suggest that gypenoside XIII can regulate lipid metabolism in fatty liver cells and improve liver fibrosis in NASH mice. Therefore, gypenoside XIII has potential as a novel agent for the treatment of NASH.

Si-Ni-San Reduces Hepatic Lipid Deposition in Rats with Metabolic Associated Fatty Liver Disease by AMPK/SIRT1 Pathway

Background

Metabolic associated fatty liver disease (MAFLD) is a chronic disease characterized by excessive lipid deposition in the liver without alcohol or other clear liver-damaging factors. AMP-activated protein kinase (AMPK)/silencing information regulator (SIRT)1 signaling pathway plays an important role in MAFLD development. Si-Ni-San (SNS), a traditional Chinese medicine, has shown reducing hepatic lipid deposition in MAFLD rats, however, the underlying mechanisms of SNS are barely understood.

Purpose

The aim of this research was to investigate the mechanisms of SNS in reducing hepatic lipid deposition in MAFLD rats by regulating AMPK/SIRT1 signaling pathways.

Methods

The components of SNS were determined by high performance liquid chromatography with mass spectrometry (HPLC-MS) analysis. MAFLD rats were induced by high-fat and high-cholesterol diet (HFHCD), and treated by SNS. SNS-containing serum and Compound C (AMPK inhibitor) were used to treat palmitic acid (PA)-induced HepG2 cells. To elucidate the potential mechanism, lipid synthesis-related proteins (SREBP-1c and FAS), fatty acid oxidation (PPARα and CPT-1), and AMPK/SIRT1 signaling pathway (p-AMPK and SIRT1) were assessed by Western blot.

Results

SNS improved serum lipid levels, liver function and reduced hepatic lipid deposition in MAFLD rats. SNS-containing serum reduced lipid deposition in PA-induced HepG2 cells. SNS could up-regulate protein expressions of PPARα, CPT-1, p-AMPK and SIRT1, and down-regulate protein expressions of SREBP-1c and FAS. Similar effects of SNS-containing serum were observed in PA-induced HepG2 cells. Meanwhile, Compound C weakened the therapeutic effects of SNS-containing serum on lipid deposition.

Conclusion

SNS could reduce hepatic lipid deposition by inhibiting lipid synthesis and promoting fatty acid oxidation, which might be related with activating the AMPK/SIRT1 signaling pathway. This study could provide a theoretical basis for the clinical use of SNS to treat MAFLD.

The Role of Fucoxanthin in Non-Alcoholic Fatty Liver Disease

Chronic liver disease (CLD) has emerged as a leading cause of human deaths. It caused 1.32 million deaths in 2017, which affected men more than women by a two-to-one ratio. There are various causes of CLD, including obesity, excessive alcohol consumption, and viral infection. Among them, non-alcoholic fatty liver disease (NAFLD), one of obesity-induced liver diseases, is the major cause, representing the cause of more than 50% of cases. Fucoxanthin, a carotenoid mainly found in brown seaweed, exhibits various biological activities against NAFLD. Its role in NAFLD appears in several mechanisms, such as inducing thermogenesis in mitochondrial homeostasis, altering lipid metabolism, and promoting anti-inflammatory and anti-oxidant activities. The corresponding altered signaling pathways are the β3-adorenarine receptor (β3Ad), proliferator-activated receptor gamma coactivator (PGC-1), adenosine monophosphate-activated protein kinase (AMPK), peroxisome proliferator-activated receptor (PPAR), sterol regulatory element binding protein (SREBP), nuclear factor kappa B (NF-κB), mitogen-activated protein kinase (MAPK), protein kinase B (AKT), SMAD2/3, and P13K/Akt pathways. Fucoxanthin also exhibits anti-fibrogenic activity that prevents non-alcoholic steatohepatitis (NASH) development.

A Review of the Effects of Fucoxanthin on NAFLD

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent form of chronic liver disease. Fucoxanthin, a red-orange marine carotenoid, is found in natural marine seaweeds with high antioxidant activity and several other remarkable biological features. The aim of this review is to gather evidence of the positive benefits of fucoxanthin on NAFLD. Fucoxanthin provides an extensive list of physiological and biological properties, such as hepatoprotective, anti-obesity, anti-tumor, and anti-diabetes properties, in addition to antioxidant and anti-inflammatory properties. This review focuses on published research on the preventative effects of fucoxanthin on NAFLD from the perspective of human clinical trials, animal experiments in vivo, and in vitro cell investigations. Using a variety of experimental designs, including treatment dosage, experiment model, and experimental periods, the positive effects of fucoxanthin were demonstrated. Fucoxanthin's biological activities were outlined, with an emphasis on its therapeutic efficacy in NAFLD. Fucoxanthin showed beneficial effects in modulating lipid metabolism, lipogenesis, fatty acid oxidation, adipogenesis, and oxidative stress on NAFLD. A deeper comprehension of NAFLD pathogenesis is essential for the development of novel and effective therapeutic strategies.

Bioactive Compounds from Brown Algae Alleviate Nonalcoholic Fatty Liver Disease: An Extensive Review

Nonalcoholic fatty liver disease (NAFLD) is one of the most prevalent chronic liver diseases. The increasing NAFLD incidences are associated with unhealthy lifestyles. Currently, there are no effective therapeutic options for NAFLD. Thus, there is a need to develop safe, efficient, and economic treatment options for NAFLD. Brown algae, which are edible, contain abundant bioactive compounds, including polysaccharides and phlorotannins. They have been shown to ameliorate insulin resistance, as well as hepatic steatosis, and all of these biological functions can potentially alleviate NAFLD. Accumulating reports have shown that increasing dietary consumption of brown algae reduces the risk for NAFLD development. In this review, we summarized the animal experiments and clinical proof of brown algae and their bioactive compounds for NAFLD treatment within the past decade. Our findings show possible avenues for further research into the pathophysiology of NAFLD and brown algae therapy.

Inhibition Effect of Adipogenesis and Lipogenesis via Activation of AMPK in Preadipocytes Treated with Canavalia gladiata Extract

The aim of this study was to investigate the effect of Canavalia gladiata extract (CGE) on the regulation of AMP-activated protein kinase (AMPK) in 3T3-L1 preadipocytes and evaluate the adipogenesis and lipogenesis mechanisms. In 3T3-L1 preadipocytes, lipid accumulation and differentiation were suppressed by 1.1, 1.3, and 1.4 times under the CGE treatment at 0.25, 0.5, and 1.0 mg/mL, respectively. The expression of the main genes involved in the inhibition of adipogenesis was evaluated at the mRNA level via a transcription-polymerase chain reaction. The extract at 1.0 mg/mL increased the mRNA expressions of AMPK and carnitine palmitoyl transferase-1 (CPT-1) by 1.9 and 1.2 times, respectively, while it decreased the expression of sterol regulatory element binding proteins-1c (SREBP-1c), peroxisome proliferator activated receptor-γ (PPAR-γ), CCAAT enhancer binding protein-α (C/EBP-α), and fatty acid synthase (FAS) by 1.1, 1.2, 1.8, and 1.5 times, respectively, indicating inhibition of the adipogenesis and lipogenesis potential of CGE. Gallic acid (4.02 mg/g) was identified as the main component of the CGE via LC-MS/MS and HPLC analysis. The results of this study suggested that CGE can be utilized as an anti-obesity food additive or medication by activating the AMPK-induced regulation and suppressing adipogenesis transcription factors.

Application of In Vitro Models for Studying the Mechanisms Underlying the Obesogenic Action of Endocrine-Disrupting Chemicals (EDCs) as Food Contaminants-A Review

Obesogenic endocrine-disrupting chemicals (EDCs) belong to the group of environmental contaminants, which can adversely affect human health. A growing body of evidence supports that chronic exposure to EDCs can contribute to a rapid increase in obesity among adults and children, especially in wealthy industrialized countries with a high production of widely used industrial chemicals such as plasticizers (bisphenols and phthalates), parabens, flame retardants, and pesticides. The main source of human exposure to obesogenic EDCs is through diet, particularly with the consumption of contaminated food such as meat, fish, fruit, vegetables, milk, and dairy products. EDCs can promote obesity by stimulating adipo- and lipogenesis of target cells such as adipocytes and hepatocytes, disrupting glucose metabolism and insulin secretion, and impacting hormonal appetite/satiety regulation. In vitro models still play an essential role in investigating potential environmental obesogens. The review aimed to provide information on currently available two-dimensional (2D) in vitro animal and human cell models applied for studying the mechanisms of obesogenic action of various industrial chemicals such as food contaminants. The advantages and limitations of in vitro models representing the crucial endocrine tissue (adipose tissue) and organs (liver and pancreas) involved in the etiology of obesity and metabolic diseases, which are applied to evaluate the effects of obesogenic EDCs and their disruption activity, were thoroughly and critically discussed.

Advances in Fucoxanthin Research for the Prevention and Treatment of Inflammation-Related Diseases

Owing to its unique structure and properties, fucoxanthin (FX), a carotenoid, has attracted significant attention. There have been numerous studies that demonstrate FX's anti-inflammatory, antioxidant, antitumor, and anti-obesity properties against inflammation-related diseases. There is no consensus, however, regarding the molecular mechanisms underlying this phenomenon. In this review, we summarize the potential health benefits of FX in inflammatory-related diseases, from the perspective of animal and cellular experiments, to provide insights for future research on FX. Previous work in our lab has demonstrated that FX remarkably decreased LPS-induced inflammation and improved survival in septic mice. Further investigation of the activity of FX against a wide range of diseases will require new approaches to uncover its molecular mechanism. This review will provide an outline of the current state of knowledge regarding FX application in the clinical setting and suggest future directions to implement FX as a therapeutic ingredient in pharmaceutical sciences in order to develop it into a treatment strategy against inflammation-associated disorders.

Fucoxanthin: A Promising Phytochemical on Diverse Pharmacological Targets

Fucoxanthin (FX) is a special carotenoid having an allenic bond in its structure. FX is extracted from a variety of algae and edible seaweeds. It has been proved to contain numerous health benefits and preventive effects against diseases like diabetes, obesity, liver cirrhosis, malignant cancer, etc. Thus, FX can be used as a potent source of both pharmacological and nutritional ingredient to prevent infectious diseases. In this review, we gathered the information regarding the current findings on antimicrobial, antioxidant, anti-inflammatory, skin protective, anti-obesity, antidiabetic, hepatoprotective, and other properties of FX including its bioavailability and stability characteristics. This review aims to assist further biochemical studies in order to develop further pharmaceutical assets and nutritional products in combination with FX and its various metabolites.

Integration of bioassay and non-target metabolite analysis of tomato reveals that β-carotene and lycopene activate the adiponectin signaling pathway, including AMPK phosphorylation

Adiponectin, an adipokine, regulates glucose metabolism and insulin sensitivity through the adiponectin receptor (AdipoR). In this study, we searched for metabolites that activate the adiponectin signaling pathway from tomato (Solanum lycopersicu). Metabolites of mature tomato were separated into 55 fractions by liquid chromatography, and then each fraction was examined using the phosphorylation assay of AMP-protein kinase (AMPK) in C2C12 myotubes and in AdipoR-knockdown cells by small interfering RNA (siRNA). Several fractions showed AMPK phosphorylation in C2C12 myotubes and siRNA-mediated abrogation of the effect. Non-targeted metabolite analysis revealed the presence of 721 diverse metabolites in tomato. By integrating the activity of fractions on AMPK phosphorylation and the 721 metabolites based on their retention times of liquid chromatography, we performed a comprehensive screen for metabolites that possess adiponectin-like activity. As the screening suggested that the active fractions contained four carotenoids, we further analyzed β-carotene and lycopene, the major carotenoids of food. They induced AMPK phosphorylation via the AdipoR, Ca²⁺/calmodulin-dependent protein kinase kinase and Ca²⁺ influx, in addition to activating glucose uptake via AdipoR in C2C12 myotubes. All these events were characteristic adiponectin actions. These results indicated that the food-derived carotenoids, β-carotene and lycopene, activate the adiponectin signaling pathway, including AMPK phosphorylation.

A Systematic Review on Marine Algae-Derived Fucoxanthin: An Update of Pharmacological Insights

Fucoxanthin, belonging to the xanthophyll class of carotenoids, is a natural antioxidant pigment of marine algae, including brown macroalgae and diatoms. It represents 10% of the total carotenoids in nature. The plethora of scientific evidence supports the potential benefits of nutraceutical and pharmaceutical uses of fucoxanthin for boosting human health and disease management. Due to its unique chemical structure and action as a single compound with multi-targets of health effects, it has attracted mounting attention from the scientific community, resulting in an escalated number of scientific publications from January 2017 to February 2022. Fucoxanthin has remained the most popular option for anti-cancer and anti-tumor activity, followed by protection against inflammatory, oxidative stress-related, nervous system, obesity, hepatic, diabetic, kidney, cardiac, skin, respiratory and microbial diseases, in a variety of model systems. Despite much pharmacological evidence from in vitro and in vivo findings, fucoxanthin in clinical research is still not satisfactory, because only one clinical study on obesity management was reported in the last five years. Additionally, pharmacokinetics, safety, toxicity, functional stability, and clinical perspective of fucoxanthin are substantially addressed. Nevertheless, fucoxanthin and its derivatives are shown to be safe, non-toxic, and readily available upon administration. This review will provide pharmacological insights into fucoxanthin, underlying the diverse molecular mechanisms of health benefits. However, it requires more activity-oriented translational research in humans before it can be used as a multi-target drug.

Fucoxanthin Attenuates Free Fatty Acid-Induced Nonalcoholic Fatty Liver Disease by Regulating Lipid Metabolism/Oxidative Stress/Inflammation via the AMPK/Nrf2/TLR4 Signaling Pathway

Fucoxanthin, a xanthophyll carotenoid abundant in brown algae, is reported to have several biological functions, such as antioxidant, anti-inflammatory, and anti-tumor activities, in mice. We investigated the effects and mechanisms of fucoxanthin in the mixture oleate/palmitate = 2/1(FFA)-induced nonalcoholic fatty liver disease (NAFLD) cell model in this study. The results showed that the content of superoxide dismutase in the FFA group was 9.8 ± 1.0 U/mgprot, while that in the fucoxanthin high-dose (H-Fx) group (2 μg/mL) increased to 22.9 ± 0.6 U/mgprot. The content of interleukin-1β in the FFA group was 89.3 ± 3.6 ng/mL, while that in the H-Fx group was reduced to 53.8 ± 2.8 ng/mL. The above results indicate that fucoxanthin could alleviate the FFA-induced oxidative stress and inflammatory levels in the liver cells. Oil red-O staining revealed visible protrusions and a significant decrease in the number of lipid droplets in the cytoplasm of cells in the fucoxanthin group. These findings on the mechanisms of action suggest that fucoxanthin can repair FFA-induced NAFLD via the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway and nuclear factor erythroid-2-related factor 2-mediated (Nrf2) signaling pathway, as well as by downregulating the expression of the Toll-like receptor 4-mediated (TLR4) signaling pathway. Fucoxanthin exhibited alleviating effects in the FFA-induced NAFLD model and could be explored as a potential anti-NAFLD substance.

Heat-Killed Enterococcus faecalis EF-2001 Attenuate Lipid Accumulation in Diet-Induced Obese (DIO) Mice by Activating AMPK Signaling in Liver

To explore the inhibitory mechanism of heat-killed Enterococcus faecalis, EF-2001 on hepatic lipid deposition, a diet-induced obese (DIO) animal model was established by high-fat diet (HFD). The DIO C57BL/6 mice were divided into four groups: the normal group without HFD (ND, n = 8), obesity group (HFD, n = 8), experimental group (HFD + EF-2001, 200 mg/kg, n = 8), and positive control group (HFD + Orlistat, 60 mg/kg, n = 8). After 4 weeks, liver and adipose tissue were fixed in 10% paraformaldehyde, followed by embedding in paraffin for tissue sectioning. The differences in body mass, body fat ratio, fatty cell area, and lipid profiling of the liver (TC, LDL, and HDL) were also determined. Moreover, Western blot was performed to analyze the expression of lipid accumulation-related proteins, including AMPK，PPARγ, SREBP-1, ACC, and FAS. Compared with the HFD group, the HFD + EF-2001 group exhibited decreased fat mass, liver index, adipocyte area, TC, and LDL, and an increased level of HDL. The results of liver hematoxylin and eosin (H&E), and oil red O staining showed that the mice in each intervention group were improved on hepatic lipid accumulation, and the mice in the HFD + EF-2001 group were the most similar to those in the normal group when compared with the HFD group. From the Western blot results, we proved that EF-2001 activated the AMPK signaling pathway. EF-2001 significantly upregulated the expressions of p-AMPK and p-ACC and downregulated PPARγ, SREBP-1, and FAS in murine liver. Taken together, these results suggest that EF-2001 decrease lipid accumulation in the DIO model mice through the AMPK pathway and ameliorate liver damage by HFD.

Fucoxanthin Attenuates Oxidative Damage by Activating the Sirt1/Nrf2/HO-1 Signaling Pathway to Protect the Kidney from Ischemia-Reperfusion Injury

Oxidative stress is a key component of renal ischemia/reperfusion (I/R) injury. Fucoxanthin (Fx), a marine carotenoid with enhanced antioxidant capacity, acts as a ROS inhibitor in diseases such as ischemic stroke and acute lung injury. We hypothesized that fucoxanthin could attenuate renal I/R-induced oxidative damage. C57BL/6 mice ( $n=30$ ) were randomly assigned to sham, IR, $\text{IR}+\text{DMSO}$ , and $\text{IR}+\text{Fx}$ (25, 50, and 100 mg/kg) groups. The renal I/R injury was induced by clamping the left kidney nephron tip in mice. Fucoxanthin was injected intraperitoneally 24 hours before surgery. Compared with the IR group, pretreatment with fucoxanthin significantly improved renal dysfunction and tissue structural damage and inhibited ROS levels and apoptosis. Consistent results were observed in HK-2 cells. Besides, we found that renal I/R resulted in decreased expression of Sirt1, Nrf2, and HO-1, while fucoxanthin upregulated the expression of Sirt1, Nrf2, and HO-1. The protective effects of fucoxanthin were significantly reversed by EX527 (a selective inhibitor of Sirt1) or si-Sirt1. In conclusion, our study investigated the protective effect of fucoxanthin against renal I/R injury, and the underlying mechanism may be related to the activation of the Sirt1/Nrf2/HO-1 signaling pathway by fucoxanthin to attenuate oxidative stress-induced apoptosis.

Lipid-Lowering Bioactivity of Microalga Nitzschia laevis Extract Containing Fucoxanthin in Murine Model and Carcinomic Hepatocytes

Non-alcoholic fatty liver disease (NAFLD), characterized by hepatic steatosis, is one of the most common liver diseases worldwide. So far, no definitive medical treatment has been established to treat NAFLD except for lifestyle medication. Nitzschia laevis extract (NLE), a microalgal extract rich in fucoxanthin, has been previously demonstrated to reduce bodyweight in high-fat-diet (HFD) C57BL/6J mice, indicating potential for prevention of NAFLD. In the present study, we investigated the lipid-lowering effects of NLE in HFD-induced steatosis murine model and palmitate-treated HepG2 cells. The results showed that NLE significantly lowered inguinal fat and attenuated hepatic steatosis in C57BL/6J mice. Especially, NLE significantly prevented lipid accumulation in HepG2 cells. This was probably due to its capability to enhance hepatic mitochondrial function as evidenced by the increased oxygen consumption rate (OCR) and mitochondrial membrane potential (MMP), and repress fatty acid synthesis through phosphorylation of acetyl-CoA carboxylase (ACC). Moreover, fucoxanthin was identified to be responsible for the lipid-lowering effect of NLE. Taken together, NLE or other microalgal fucoxanthin-rich products are promising natural products that may help prevent against NAFLD.

Anti-Inflammatory and Anticancer Effects of Microalgal Carotenoids

Acute inflammation is a key component of the immune system’s response to pathogens, toxic agents, or tissue injury, involving the stimulation of defense mechanisms aimed to removing pathogenic factors and restoring tissue homeostasis. However, uncontrolled acute inflammatory response may lead to chronic inflammation, which is involved in the development of many diseases, including cancer. Nowadays, the need to find new potential therapeutic compounds has raised the worldwide scientific interest to study the marine environment. Specifically, microalgae are considered rich sources of bioactive molecules, such as carotenoids, which are natural isoprenoid pigments with important beneficial effects for health due to their biological activities. Carotenoids are essential nutrients for mammals, but they are unable to synthesize them; instead, a dietary intake of these compounds is required. Carotenoids are classified as carotenes (hydrocarbon carotenoids), such as α- and β-carotene, and xanthophylls (oxygenate derivatives) including zeaxanthin, astaxanthin, fucoxanthin, lutein, α- and β-cryptoxanthin, and canthaxanthin. This review summarizes the present up-to-date knowledge of the anti-inflammatory and anticancer activities of microalgal carotenoids both in vitro and in vivo, as well as the latest status of human studies for their potential use in prevention and treatment of inflammatory diseases and cancer.

Marine Natural Products and Coronary Artery Disease

Coronary artery disease is the major cause of mortality worldwide, especially in low- and middle-income earners. To not only reduce angina symptoms and exercise-induced ischemia but also prevent cardiovascular events, pharmacological intervention strategies, including antiplatelet drugs, anticoagulant drugs, statins, and other lipid-lowering drugs, and renin-angiotensin-aldosterone system blockers, are conducted. However, the existing drugs for coronary artery disease are incomprehensive and have some adverse reactions. Thus, it is necessary to look for new drug research and development. Marine natural products have been considered a valuable source for drug discovery because of their chemical diversity and biological activities. The experiments and investigations indicated that several marine natural products, such as organic small molecules, polysaccharides, proteins, and bioactive peptides, and lipids were effective for treating coronary artery disease. Here, we particularly discussed the functions and mechanisms of active substances in coronary artery disease, including antiplatelet, anticoagulant, lipid-lowering, anti-inflammatory, and antioxidant activities.

Kaempferol and Kaempferide Attenuate Oleic Acid-Induced Lipid Accumulation and Oxidative Stress in HepG2 Cells

Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases which lacks ideal treatment options. Kaempferol and kaempferide, two natural flavonol compounds isolated from Hippophae rhamnoides L., were reported to exhibit a strong regulatory effect on lipid metabolism, for which the mechanism is largely unknown. In the present study, we investigated the effects of kaempferol and kaempferide on oleic acid (OA)-treated HepG2 cells, a widely used in vitro model of NAFLD. The results indicated an increased accumulation of lipid droplets and triacylglycerol (TG) by OA, which was attenuated by kaempferol and kaempferide (5, 10 and 20 μM). Western blot analysis demonstrated that kaempferol and kaempferide reduced expression of lipogenesis-related proteins, including sterol regulatory element-binding protein 1 (SREBP1), fatty acid synthase (FAS) and stearoyl-CoA desaturase 1 (SCD-1). Expression of peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT enhancer binding proteins β (C/EBPβ), two adipogenic transcription factors, was also decreased by kaempferol and kaempferide treatment. In addition, western blot analysis also demonstrated that kaempferol and kaempferide reduced expression of heme oxygenase-1 (HO-1) and nuclear transcription factor-erythroid 2-related factor 2 (Nrf2). Molecular docking was performed to identify the direct molecular targets of kaempferol and kaempferide, and their binding to SCD-1, a critical regulator in lipid metabolism, was revealed. Taken together, our findings demonstrate that kaempferol and kaempferide could attenuate OA-induced lipid accumulation and oxidative stress in HepG2 cells, which might benefit the treatment of NAFLD.

Fucoxanthin Ameliorates Oxidative Stress and Airway Inflammation in Tracheal Epithelial Cells and Asthmatic Mice

Fucoxanthin is isolated from brown algae and was previously reported to have multiple pharmacological effects, including anti-tumor and anti-obesity effects in mice. Fucoxanthin also decreases the levels of inflammatory cytokines in the bronchoalveolar lavage fluid (BALF) of asthmatic mice. The purpose of the present study was to investigate the effects of fucoxanthin on the oxidative and inflammatory responses in inflammatory human tracheal epithelial BEAS-2B cells and attenuated airway hyperresponsiveness (AHR), airway inflammation, and oxidative stress in asthmatic mice. Fucoxanthin significantly decreased monocyte cell adherence to BEAS-2B cells. In addition, fucoxanthin inhibited the production of pro-inflammatory cytokines, eotaxin, and reactive oxygen species in BEAS-2B cells. Ovalbumin (OVA)-sensitized mice were treated by intraperitoneal injections of fucoxanthin (10 mg/kg or 30 mg/kg), which significantly alleviated AHR, goblet cell hyperplasia and eosinophil infiltration in the lungs, and decreased Th2 cytokine production in the BALF. Furthermore, fucoxanthin significantly increased glutathione and superoxide dismutase levels and reduced malondialdehyde (MDA) levels in the lungs of asthmatic mice. These data demonstrate that fucoxanthin attenuates inflammation and oxidative stress in inflammatory tracheal epithelial cells and improves the pathological changes related to asthma in mice. Thus, fucoxanthin has therapeutic potential for improving asthma.

Fucoxanthin rescues dexamethasone induced C2C12 myotubes atrophy

Muscle atrophy and weakness are the adverse effects of long-term or high dose usage of glucocorticoids. In the present study, we explored the effects of fucoxanthin (10 μM) on dexamethasone (10 μM)-induced atrophy in C2C12 myotubes and investigated its underlying mechanisms. The diameter of myotubes was observed under a light microscope, and the expression of myosin heavy chain (MyHC), proteolysis-related, autophagy-related, apoptosis-related, and mitochondria-related proteins was analyzed by western blots or immunoprecipitation. Fucoxanthin alleviates dexamethasone-induced muscle atrophy in C2C12 myotubes, indicated by increased myotubes diameter and expression of MyHC, decreased expression of muscle atrophy F-box (Atrogin-1) and muscle ring finger 1 (MuRF1). Through activating SIRT1, fucoxanthin inhibits forkhead box O (FoxO) transcriptional activity to reduce protein degradation, induces autophagy to enhance degraded protein clearance, promotes mitochondrial function and diminishes apoptosis. In conclusion, we identified fucoxanthin ameliorates dexamethasone induced C2C12 myotubes atrophy through SIRT1 activation.

The Marine Microalga, Tisochrysis lutea, Protects against Metabolic Disorders Associated with Metabolic Syndrome and Obesity

Long-chain polyunsaturated fatty acids n-3 series and especially docosahexaenoic acid are known to exert preventive effects on metabolic disturbances associated with obesity and decrease cardiovascular disease risk. n-3 LC-PUFAs are mainly consumed in the form of fish oil, while other sources, such as certain microalgae, may contain a high content of these fatty acids. The aim of this study was to evaluate the effects of Tisochrysis lutea (Tiso), a microalga rich in DHA, on metabolic disorders associated with obesity. Three male Wistar rat groups were submitted for eight weeks to a standard diet or high-fat and high fructose diet (HF), supplemented or not with 12% of T. lutea (HF-Tiso). The supplementation did not affect plasma alanine aminotransferase (ALAT). Bodyweight, glycemia and insulinemia decreased in HF-Tiso rats (ANOVA, p < 0.001), while total plasma cholesterol, high-density lipoprotein-cholesterol (HDL-C) increased (ANOVA, p < 0.001) without change of low-density lipoprotein-cholesterol (LDL-C) and triacylglycerol (TAG) levels. Tiso supplementation decreased fat mass and leptinemia as well as liver TAG, cholesterol and plasma tumor necrosis factor-alpha levels (ANOVA, p < 0.001) while it did not affect interleukin 6 (IL-6), IL-4 and lipopolysaccharides levels. HF-Tiso rats showed an increase of IL-10 level in abdominal adipose tissue (ANOVA, p < 0.001). In conclusion, these results indicated that DHA-rich T. lutea might be beneficial for the prevention of obesity and improvement of lipid and glucose metabolism.

Advances in Studies on the Pharmacological Activities of Fucoxanthin

Fucoxanthin is a natural carotenoid derived mostly from many species of marine brown algae. It is characterized by small molecular weight, is chemically active, can be easily oxidized, and has diverse biological activities, thus protecting cell components from ROS. Fucoxanthin inhibits the proliferation of a variety of cancer cells, promotes weight loss, acts as an antioxidant and anti-inflammatory agent, interacts with the intestinal flora to protect intestinal health, prevents organ fibrosis, and exerts a multitude of other beneficial effects. Thus, fucoxanthin has a wide range of applications and broad prospects. This review focuses primarily on the latest progress in research on its pharmacological activity and underlying mechanisms.

The Inhibitory Effects of Juglanin on Adipogenesis in 3T3-L1 Adipocytes

Introduction

Deregulation of adipogenesis plays an important role in obesity and other metabolism disorders. PPAR, C/EBP and SREBP1c are key transcriptional factors involved in adipogenesis and lipogenesis. Juglanin is a natural compound belonging to flavonoids, and it has been reported that juglanin has a potent inhibitory effect on inflammation and certain type of cancers. However, the effects of juglanin in adipogenesis have not been reported before.

Materials and Methods

3T3-L1 preadipocytes were incubated with differentiation induction medium in the presence or absence of 0.5, 2.5, or 5 µM juglanin for an 8-day differentiation period. The lipid droplets accumulated in the cytoplasm were monitored by Oil Red O staining on days 0, 2, 5, and 8. The regulatory effects of juglanin on adipogenesis-related genes and proteins were investigated by real-time polymerase chain reaction and Western blot analysis.

Results

Juglanin significantly decreased lipid accumulation in differentiated adipocytes. Our findings show that juglanin reduced the expression of C/EBPα, C/EBPβ, and SREBP-1c without affecting PPARα or PPARγ expression. Additionally, juglanin increased the activation of the SIRT1/AMPK signaling pathway through the phosphorylation of AMPKα. Finally, we performed an AMPK inhibitor experiment, which revealed that the inhibitory effects of juglanin on adipogenesis are mediated through AMPK.

Discussion

Juglanin can prevent adipogenesis by suppressing lipid accumulation and the differentiation of preadipocytes. The mechanism of juglanin regulating adipogenesis requires further investigation. Future clinical study in vivo could shed more light on its implication in modulating obesity and metabolic disorders.

Potential Anti-Aging Substances Derived from Seaweeds

Aging is a major risk factor for many chronic diseases, such as cancer, cardiovascular disease, and diabetes. The exact mechanisms underlying the aging process are not fully elucidated. However, a growing body of evidence suggests that several pathways, such as sirtuin, AMP-activated protein kinase, insulin-like growth factor, autophagy, and nuclear factor erythroid 2-related factor 2 play critical roles in regulating aging. Furthermore, genetic or dietary interventions of these pathways can extend lifespan by delaying the aging process. Seaweeds are a food source rich in many nutrients, including fibers, polyunsaturated fatty acids, vitamins, minerals, and other bioactive compounds. The health benefits of seaweeds include, but are not limited to, antioxidant, anti-inflammatory, and anti-obese activities. Interestingly, a body of studies shows that some seaweed-derived extracts or isolated compounds, can modulate these aging-regulating pathways or even extend lifespans of various animal models. However, few such studies have been conducted on higher animals or even humans. In this review, we focused on potential anti-aging bioactive substances in seaweeds that have been studied in cells and animals mainly based on their anti-aging cellular and molecular mechanisms.

Fucoxanthin Mitigates Subarachnoid Hemorrhage-Induced Oxidative Damage via Sirtuin 1-Dependent Pathway

Oxidative stress is a key component of the pathological cascade in subarachnoid hemorrhage (SAH). Fucoxanthin (Fx) possesses a strong antioxidant property and has shown neuroprotective effects in acute brain injuries such as ischemic stroke and traumatic brain injury. Here, we investigated the beneficial effects of Fx against SAH-induced oxidative insults and the possible molecular mechanisms. Our data showed that Fx could significantly inhibit SAH-induced reactive oxygen species production and lipid peroxidation, and restore the impairment of endogenous antioxidant enzymes activities. In addition, Fx supplementation improved mitochondrial morphology, ameliorated neural apoptosis, and reduced brain edema after SAH. Moreover, Fx administration exerted an improvement in short-term and long-term neurobehavior functions after SAH. Mechanistically, Fx inhibited oxidative damage and brain injury after SAH by deacetylation of forkhead transcription factors of the O class and p53 via sirtuin 1 (Sirt1) activation. EX527, a selective Sirt1 inhibitor, significantly abated Fx-induced Sirt1 activation and abrogated the antioxidant and neuroprotective effects of Fx after SAH. In primary neurons, Fx similarly suppressed oxidative insults and improved cell viability. These effects were associated with Sirt1 activation and were reversed by EX527 treatment. Taken together, our study explored that Fx provided protection against SAH-induced oxidative insults by inducing Sirt1 signaling, indicating that Fx might serve as a potential therapeutic drug for SAH.

Advances in the Study of Marine Products with Lipid-Lowering Properties

With twice the number of cancer's deaths, cardiovascular diseases have become the leading cause of death worldwide. Atherosclerosis, in particular, is a progressive, chronic inflammatory cardiovascular disease caused by persistent damage to blood vessels due to elevated cholesterol levels and hyperlipidemia. This condition is characterized by an increase in serum cholesterol, triglycerides, and low-density lipoprotein, and a decrease in high-density lipoprotein. Although existing therapies with hypolipidemic effects can improve the living standards of patients with cardiovascular diseases, the drugs currently used in clinical practice have certain side effects, which insists on the need for the development of new types of drugs with lipid-lowering effects. Some marine-derived substances have proven hypolipidemic activities with fewer side effects and stand as a good alternative for drug development. Recently, there have been thousands of studies on substances with lipid-lowering properties of marine origin, and some are already implemented in clinical practice. Here, we summarize the active components of marine-derived products having a hypolipidemic effect. These active constituents according to their source are divided into algal, animal, plant and microbial and contribute to the development and utilization of marine medicinal products with hypolipidemic effects.

Effect of Carotenoids from Phaeodactylum tricornutum on Palmitate-Treated HepG2 Cells

Non-alcoholic fatty liver disease represents the most common liver disease and is characterized by an excess of lipid accumulation in hepatocytes, mainly stored as triglycerides. Phaeodactylum tricornutum is a marine microalga, which is rich in bioactive molecules known to be hepatoprotective, such as n-3 long-chain polyunsaturated fatty acids and fucoxanthin. The aim of this study was to investigate the effects of a carotenoid extract from P. tricornutum in a cellular model of non-alcoholic fatty liver disease induced by palmitate treatment. The combined effects of carotenoids and lipids, especially n-3 long-chain polyunsaturated fatty acids, were also investigated by using a total lipophilic extract. HepG2 cells were exposed for 24 h to 250 µM palmitate with or without the addition of carotenoid extract (6 μg/mL) or total lipophilic extract (100 μg/mL). The addition of carotenoid extract or total lipophilic extract prevented the accumulation of triglycerides, total cholesterol and cholesterol esters. The carotenoid extract and total lipophilic extract also decreased the mRNA expression levels of genes involved in lipogenesis (ACACA, FASN, SCD and DGAT1) and cholesterol esterification (ACAT1/SOAT1). In addition, the total lipophilic extract also downregulated the LXR/NR1H3 and SREBF1 genes, which are involved in lipogenesis regulation. By contrast, the carotenoid extract increased the mRNA level of CPT1A, a β-oxidation related gene, and reduced the lipid droplet accumulation. In conclusion, this study highlights the preventive effects against non-alcoholic fatty liver disease of the two microalga extracts.

Undaria pinnatifida extract feeding increases exercise endurance and skeletal muscle mass by promoting oxidative muscle remodeling in mice

Dietary habits can alter the skeletal muscle performance and mass, and Undaria pinnatifida extracts are considered a potent candidate for improving the muscle mass and function. Therefore, in this study, we aimed to assess the effect of U pinnatifida extracts on exercise endurance and skeletal muscle mass. C57BL/6 mice were fed a 0.25% U pinnatifida extract-containing diet for 8 weeks. U pinnatifida extract-fed mice showed increased running distance, total running time, and extensor digitorum longus and gastrocnemius muscle weights. U pinnatifida extract supplementation upregulated the expression of myocyte enhancer factor 2C, oxidative muscle fiber markers such as myosin heavy chain 1 (MHC1), and oxidative biomarkers in the gastrocnemius muscles. Compared to the controls, U pinnatifida extract-fed mice showed larger mitochondria and increased gene and protein expression of molecules involved in mitochondrial biogenesis and oxidative phosphorylation, including nuclear respiratory factor 2 and mitochondrial transcription factor A. U pinnatifida extract supplementation also increased the mRNA expression of angiogenesis markers, including VEGFa, VEGFb, FGF1, angiopoietin 1, and angiopoietin 2, in the gastrocnemius muscles. Importantly, U pinnatifida extracts upregulated the estrogen-related receptor γ and peroxisome proliferator-activated receptor gamma co-activator 1-alpha (PGC-1α)/AMP-activated protein kinase (AMPK)/sirtuin 1 (SIRT1) networks, which are partially increased by fucoxanthin, hesperetin, and caffeic acid treatments. Collectively, U pinnatifida extracts enhance mitochondrial biogenesis, increase oxidative muscle fiber, and promote angiogenesis in skeletal muscles, resulting in improved exercise capacity and skeletal muscle mass. These effects are attributable to fucoxanthin, hesperetin, and caffeic acid, bioactive components of U pinnatifida extracts.

Fucoxanthin inhibits hepatic oxidative stress, inflammation, and fibrosis in diet-induced nonalcoholic steatohepatitis model mice

Nonalcoholic steatohepatitis (NASH) is associated with hepatocyte injury, excessive oxidative stress, and chronic inflammation in fatty liver, and can progress to more severe liver diseases, such as cirrhosis and hepatocellular carcinoma. However, currently there are no effective therapies for NASH. Marine carotenoid, fucoxanthin (Fx), abundant in brown seaweeds, has variable biological properties, such as anti-cancer, anti-inflammatory, anti-oxidative and anti-obesity. However, the effect of Fx on the development of NASH has not been explored. We investigated the protective effects of Fx in diet-induced NASH model mice fed choline-deficient L-amino acid-defined high fat diet (CDAHFD). Fx administration significantly attenuated liver weight gain and hepatic fat accumulation, resulting in the alleviation of hepatic injury. Furthermore, the Fx-fed mice, not only exhibited reduced hepatic lipid oxidation, but also decreased mRNA expression levels of inflammation and infiltration-related genes compared to that of the CDAHFD-fed mice. Moreover, fucoxanthinol and amarouciaxanthin A, two Fx metabolites exerted anti-inflammatory effects in the liver via inhibiting the chemokine production in hepatocytes. In case of fibrosis, one of the features of advanced NASH, the expression of fibrogenic factors including activated-hepatic stellate cell marker was significantly decreased in the liver of Fx-fed mice. Thus, the present study elucidated that dietary Fx not only inhibited hepatic oxidative stress and inflammation but also prevented early phase of fibrosis in the diet-induced NASH model mice.

Fucoxanthin: A promising compound for human inflammation-related diseases

Fucoxanthin, a natural product of carotenoids, is a potential drug source obtained from marine algae. The special chemical structure of fucoxanthin has equipped it with a variety of biological activities. Several studies have indicated that fucoxanthin has a potential protective effect on a variety of inflammation-related diseases. This mechanism may be related to fucoxanthin's strong antioxidant capacity and gut microbiota regulation. The key molecules that require consideration include nuclear factor erythroid 2-related factor 2, Akt serine/threonine kinase/phosphatidylinositol-3-kinase, extracellular signal-regulated kinase, adenosine monophosphate (AMP)-dependent protein kinase, cAMP response element binding protein, and peroxisome proliferator-activated receptorγcoactivator-1α. The study summarizes the recent progress in the research based on the protective effect of fucoxanthin and its related molecular mechanism, in addition to the potential use of fucoxanthin as a promising compound for human inflammation-related diseases.

Carotenoids and carotenoid conversion products in adipose tissue biology and obesity: Pre-clinical and human studies

Antiobesity activities of carotenoids and carotenoid conversion products (CCPs) have been demonstrated in pre-clinical studies, and mechanisms behind have begun to be unveiled, thus suggesting these compounds may help obesity prevention and management. The antiobesity action of carotenoids and CCPs can be traced to effects in multiple tissues, notably the adipose tissues. Key aspects of the biology of adipose tissues appear to be affected by carotenoid and CCPs, including adipogenesis, metabolic capacities for energy storage, release and inefficient oxidation, secretory function, and modulation of oxidative stress and inflammatory pathways. Here, we review the connections of carotenoids and CCPs with adipose tissue biology and obesity as revealed by cell and animal intervention studies, studies addressing the role of endogenous retinoid metabolism, and human epidemiological and intervention studies. We also consider human genetic variability influencing carotenoid and vitamin A metabolism, particularly in adipose tissues, as a potentially relevant aspect towards personalization of dietary recommendations to prevent or manage obesity and optimize metabolic health. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

Health benefits of fucoxanthin in the prevention of chronic diseases

Fucoxanthin is a xanthophyll carotenoid abundant in macroalgae, such as brown seaweeds. When fucoxanthin is consumed, it can be esterified or hydrolyzed to fucoxanthinol in the gastrointestinal tract and further converted into amarouciaxanthin A in the liver. It has a unique chemical structure that confers its biological effects. Fucoxanthin has a strong antioxidant capacity by scavenging singlet molecular oxygen and free radicals. Also, it exerts an anti-inflammatory effect. Studies have demonstrated potential health benefits of fucoxanthin for the prevention of chronic diseases, such as cancer, obesity, diabetes mellitus, and liver disease. Animal studies have shown that fucoxanthin supplementation has no adverse effects. However, investigation of the safety of fucoxanthin consumption in humans is lacking. Clinical trials are required to assess the safety of fucoxanthin in conjunction with the study of mechanisms by which fucoxanthin exhibits its health benefits. This review focuses on current knowledge of metabolism and functions of fucoxanthin with its potential health benefits. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

Differential effect of herbal tea extracts on free fatty acids-, ethanol- and acetaminophen-induced hepatotoxicity in FL83B hepatocytes

In recent years, herbal tea consumption becomes popular because of the potential health benefits and attractive flavors. However, there is also a growing concern that herbal supplements contribute to the drug-drug/drug-herb interactions and hepatotoxicity. In this study, FL83B mouse hepatocytes were used as an in vitro mode of hepatotoxicity induced by free fatty acids, including palmitic acid (PA) and oleic acid (OA), ethanol, and acetaminophen. Herbal tea extracts were obtained from eight common herbal plants, including Verbena officinalis L., Hyssopus officinalis L., Salvia officinalis L., Urtica dioica L., Hemerocallis fulva (L.) L., Citrus maxima (Burm.) Merr., Citrus limon (L.) Osbeck, and Ficus formosana Maxim. MTT assay was used to evaluate the impact of these herbal tea extracts on hepatoxocitity. We found that these herbal tea extracts per se did not exhibit hepatotoxicity, and had no effect on OA-induced hepatotoxicity. However, extracts from Verbena officinalis L., Hyssopus officinalis L., Salvia officinalis L., and Hemerocallis fulva (L.) L. exhibited protective effect against PA-induced hepatotoxicity. In addition, herbal tea extracts from Verbena officinalis L., Hyssopus officinalis L., Salvia officinalis L., Urtica dioica L., Hemerocallis fulva (L.) L., and Ficus formosana Maxim. exhibited protective effect against acetaminophen-induced hepatotoxicity. Interestingly, all these herbal tea extracts enhanced ethanol-induced hepatotoxicity. Our results suggest that herbal tea extracts have differential effects on different modes of hepatotoxicity.

Maslinic acid protects against obesity-induced nonalcoholic fatty liver disease in mice through regulation of the Sirt1/AMPK signaling pathway

Maslinic acid is a pentacyclic triterpenoid that is distributed in the peel of olives. Previous studies found that maslinic acid inhibited inflammatory response and antioxidant effects. We investigated whether maslinic acid ameliorates nonalcoholic fatty liver disease in mice with high-fat-diet (HFD)-induced obesity and evaluated the regulation of lipogenesis in hepatocytes. Male C57BL/6 mice fed a normal diet or HFD (60% fat, w/w) were tested for 16 wk. After the fourth week, mice were injected intraperitoneally with maslinic acid for 12 wk. In another experiment, HepG2 cells were treated with oleic acid to induce lipid accumulation or maslinic acid to evaluate lipogenesis. Maslinic acid significantly reduced body weight compared with HFD-fed mice. Maslinic acid reduced liver weight and liver lipid accumulation and improved hepatocyte steatosis. Furthermore, serum glucose, leptin, and free fatty acid concentrations significantly reduced, but the serum adiponectin concentration was higher, in the maslinic acid group than in the HFD group. In liver tissue, maslinic acid suppressed transcription factors involved in lipogenesis and increased adipose triglyceride lipase. In vitro, maslinic acid decreased lipogenesis by activating AMPK. These findings suggest that maslinic acid acts against hepatic steatosis by regulating enzyme activity involved in lipogenesis, lipolysis, and fatty acid oxidation in the liver.-Liou, C.-J., Dai, Y.-W., Wang, C.-L., Fang, L.-W., Huang, W.-C. Maslinic acid protects against obesity-induced nonalcoholic fatty liver disease in mice through regulation of the Sirt1/AMPK signaling pathway.

Protective Effects of Licochalcone A Ameliorates Obesity and Non-Alcoholic Fatty Liver Disease Via Promotion of the Sirt-1/AMPK Pathway in Mice Fed a High-Fat Diet

Licochalcone A is a chalcone isolated from Glycyrrhiza uralensis. It showed anti-tumor and anti-inflammatory properties in mice with acute lung injuries and regulated lipid metabolism through the activation of AMP-activated protein kinase (AMPK) in hepatocytes. However, the effects of licochalcone A on reducing weight gain and improving nonalcoholic fatty liver disease (NAFLD) are unclear. Thus, the present study investigated whether licochalcone A ameliorated weight loss and lipid metabolism in the liver of high-fat diet (HFD)-induced obese mice. Male C57BL/6 mice were fed an HFD to induce obesity and NAFLD, and then were injected intraperitoneally with licochalcone A. In another experiment, a fatty liver cell model was established by incubating HepG2 hepatocytes with oleic acid and treating the cells with licochalcone A to evaluate lipid metabolism. Our results demonstrated that HFD-induced obese mice treated with licochalcone A had decreased body weight as well as inguinal and epididymal adipose tissue weights compared with HFD-treated mice. Licochalcone A also ameliorated hepatocyte steatosis and decreased liver tissue weight and lipid droplet accumulation in liver tissue. We also found that licochalcone A significantly regulated serum triglycerides, low-density lipoprotein, and free fatty acids, and decreased the fasting blood glucose value. Furthermore, in vivo and in vitro, licochalcone A significantly decreased expression of the transcription factor of lipogenesis and fatty acid synthase. Licochalcone A activated the sirt-1/AMPK pathway to reduce fatty acid chain synthesis and increased lipolysis and β-oxidation in hepatocytes. Licochalcone A can potentially ameliorate obesity and NAFLD in mice via activation of the sirt1/AMPK pathway.

Identification of Cyanobacterial Strains with Potential for the Treatment of Obesity-Related Co-Morbidities by Bioactivity, Toxicity Evaluation and Metabolite Profiling

Obesity is a complex disease resulting in several metabolic co-morbidities and is increasing at epidemic rates. The marine environment is an interesting resource of novel compounds and in particular cyanobacteria are well known for their capacity to produce novel secondary metabolites. In this work, we explored the potential of cyanobacteria for the production of compounds with relevant activities towards metabolic diseases using a blend of target-based, phenotypic and zebrafish assays as whole small animal models. A total of 46 cyanobacterial strains were grown and biomass fractionated, yielding in total 263 fractions. Bioactivities related to metabolic function were tested in different in vitro and in vivo models. Studying adipogenic and thermogenic gene expression in brown adipocytes, lipid metabolism and glucose uptake in hepatocytes, as well as lipid metabolism in zebrafish larvae, we identified 66 (25%) active fractions. This together with metabolite profiling and the evaluation of toxicity allowed the identification of 18 (7%) fractions with promising bioactivity towards different aspects of metabolic disease. Among those, we identified several known compounds, such as eryloside T, leptosin F, pheophorbide A, phaeophytin A, chlorophyll A, present as minor peaks. Those compounds were previously not described to have bioactivities in metabolic regulation, and both known or unknown compounds could be responsible for such effects. In summary, we find that cyanobacteria hold a huge repertoire of molecules with specific bioactivities towards metabolic diseases, which needs to be explored in the future.

Fucoxanthin Protects against oxLDL-Induced Endothelial Damage via Activating the AMPK-Akt-CREB-PGC1α Pathway

SCOPE

Atherosclerotic cardiovascular disease is the most prevalent cause of mortality and morbidity. Fucoxanthin (FX) possesses anti-hypertensive and anti-obesity properties. However, the molecular mechanisms underlying the inhibitory effects of FX on oxidized low-density lipoprotein (oxLDL)-induced oxidative injuries in human endothelial cells are still largely unknown. This study aims to test the hypothesis that FX protects against oxLDL-induced oxidative stress by upregulating AMP-activated protein kinase (AMPK) and to explore the roles of cAMP response element binding protein (CREB) and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α).

METHODS AND RESULTS

Human umbilical vein endothelial cells are treated with oxLDL in the presence or absence of FX. FX significantly increases AMPK phosphorylation. In addition, FX diminishes oxLDL-mediated nicotinamide adenine dinucleotide phosphate oxidase activation by inhibiting protein kinase C and subsequently inducing reactive oxygen species generation and impairing the activity of the endogenous antioxidant enzyme superoxidase dismutase. Furthermore, FX restores oxLDL-mediated dephosphorylation of phosphoinositide-3-kinase/Akt and decreases CREB and PGC-1α expression to nearly normal levels. Moreover, FX ameliorates the oxLDL-mediated suppression of mitochondrial function and apoptosis.

CONCLUSION

These findings provide new insights into the possible molecular mechanisms by which FX mitigates oxLDL-induced endothelial oxidative stress and mitochondrial dysfunction.

Fucoxanthin prevents lipopolysaccharide-induced depressive-like behavior in mice via AMPK- NF-κB pathway

Fucoxanthin (FX), a natural carotenoid abundant in edible brown seaweeds, has been shown the great anti-oxidant, anti-inflammatory and anti-diabetic effects in vivo and in vitro. The present study was designed to investigate the effects of FX on lipopolysaccharide (LPS)-induced behavioral defects in mice. In depressive behavior tests, the increased immobility time of forced swimming test and tail suspension test by LPS treatment in mice, which were significantly reversed by FX treatment (200 mg/kg, i.g.). In anxiety behavior tests, LPS injection was neither influence the anxiety-related parameters in marble burying test nor that in elevated plus maze test. Interestingly, anxiolytic effects were observed in single FX treated control and LPS-induced mice groups. FX treatment also reversed LPS-induced body weight loss and food intake decreases. Biochemical analysis indicated that FX inhibited LPS-induced overexpression of pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α), as well as iNOS and COX-2 in the hippocampus, frontal cortex and hypothalamus, via the modulation of AMPK-NF-κB signaling pathway.

Ginkgolide C reduced oleic acid-induced lipid accumulation in HepG2 cells

Ginkgolide C, isolated from Ginkgo biloba, is a diterpene lactone that has multiple biological functions and can improve Alzheimer disease and platelet aggregation. Ginkgolide C also inhibits adipogenesis in 3T3-L1 adipocytes. The present study evaluated whether ginkgolide C reduced lipid accumulation and regulated the molecular mechanism of lipogenesis in oleic acid-induced HepG2 hepatocytes. HepG2 cells were treated with 0.5 mM oleic acid for 48 h to induce a fatty liver cell model. Then, the cells were exposed to various concentrations of ginkgolide C for 24 h. Staining with Oil Red O and the fluorescent dye BODIPY 493/503 revealed that ginkgolide C significantly reduced excessive lipid accumulation in HepG2 cells. Ginkgolide C decreased peroxisome proliferator-activated receptor γ and sterol regulatory element-binding protein 1c to block the expression of fatty acid synthase. Ginkgolide C treatment also promoted the expression of adipose triglyceride lipase and the phosphorylation level of hormone-sensitive lipase to enhance the decomposition of triglycerides. In addition, ginkgolide C stimulated CPT-1 to activate fatty acid β-oxidation, significantly increased sirt1 and phosphorylation of AMP-activated protein kinase (AMPK), and decreased expression of acetyl-CoA carboxylase for suppressed fatty acid synthesis in hepatocytes. Taken together, our results suggest that ginkgolide C reduced lipid accumulation and increased lipolysis through the sirt1/AMPK pathway in oleic acid-induced fatty liver cells.