Astaxanthin reduces hepatic lipid accumulations in high-fat-fed C57BL/6J mice via activation of peroxisome proliferator-activated receptor (PPAR) alpha and inhibition of PPAR gamma and Akt

Maintaining Effective Beta Cell Function in the Face of Metabolic Syndrome-Associated Glucolipotoxicity-Nutraceutical Options

In people with metabolic syndrome, episodic exposure of pancreatic beta cells to elevated levels of both glucose and free fatty acids (FFAs)-or glucolipotoxicity-can induce a loss of glucose-stimulated insulin secretion (GSIS). This in turn can lead to a chronic state of glucolipotoxicity and a sustained loss of GSIS, ushering in type 2 diabetes. Loss of GSIS reflects a decline in beta cell glucokinase (GK) expression associated with decreased nuclear levels of the pancreatic and duodenal homeobox 1 (PDX1) factor that drives its transcription, along with that of Glut2 and insulin. Glucolipotoxicity-induced production of reactive oxygen species (ROS), stemming from both mitochondria and the NOX2 isoform of NADPH oxidase, drives an increase in c-Jun N-terminal kinase (JNK) activity that promotes nuclear export of PDX1, and impairs autocrine insulin signaling; the latter effect decreases PDX1 expression at the transcriptional level and up-regulates beta cell apoptosis. Conversely, the incretin hormone glucagon-like peptide-1 (GLP-1) promotes nuclear import of PDX1 via cAMP signaling. Nutraceuticals that quell an increase in beta cell ROS production, that amplify or mimic autocrine insulin signaling, or that boost GLP-1 production, should help to maintain GSIS and suppress beta cell apoptosis in the face of glucolipotoxicity, postponing or preventing onset of type 2 diabetes. Nutraceuticals with potential in this regard include the following: phycocyanobilin-an inhibitor of NOX2; agents promoting mitophagy and mitochondrial biogenesis, such as ferulic acid, lipoic acid, melatonin, berberine, and astaxanthin; myo-inositol and high-dose biotin, which promote phosphatidylinositol 3-kinase (PI3K)/Akt activation; and prebiotics/probiotics capable of boosting GLP-1 secretion. Complex supplements or functional foods providing a selection of these agents might be useful for diabetes prevention.

Astaxanthin attenuates hepatic steatosis in high-fat diet-fed rats by suppressing microRNA-21 via transactivation of nuclear factor erythroid 2-related factor 2

This study examined whether astaxanthin (ASX) could alleviate hepatic steatosis in rats fed a high-fat diet (HFD) by modulating the nuclear factor erythroid 2-related factor 2 (Nrf2)/miR-21 axis. Rats (n = 8/group) were fed either a standard diet (3.8 kcal/g; 10% fat) or HFD (4.6 kcal/g; 40% fat) and treated orally with either the vehicle or ASX (6 mg/kg) daily for 8 days. Another group was fed HFD and treated with ASX and brusatol (an Nrf2 inhibitor) (2 mg/kg/twice per week/i.p.). ASX prevented the gain in body and liver weights and attenuated hepatic lipid accumulation in HFD-fed rats. In the control and HFD-fed rats, ASX did not affect food intake, serum free fatty acid (FFA) content, and glucose and insulin levels and tolerance. However, serum triglyceride (TG), cholesterol, and low-density lipoprotein-cholesterol levels; hepatic levels of TGs and FFAs; and hepatic levels of Srebp1, Srebp2, HMGCR, and fatty acid synthase mRNAs and miR-21 were reduced and the mRNA levels of Pparα were significantly increased in both the groups. These effects were associated with a reduction in the hepatic levels of reactive oxygen species, malondialdehyde, tumor necrosis factor-α, and interlukin-6 as well as an increase in superoxide dismutase levels, total glutathione content, and nuclear levels and activity of Nrf2. miR-21 levels were strongly correlated with the nuclear activity of Nrf2. Brusatol completely reversed the effects of ASX. In conclusion, ASX prevents hepatic steatosis mainly by transactivating Nrf2 and is associated with the suppression of miR-21 and Srebp1/2 and upregulation of Pparα expression.

Microbial Composition and Co-occurrence Patterns in the Gut Microbial Community of Normal and Obese Mice in Response to Astaxanthin

The changes and interaction of gut microbiota, which respond to dietary supplements, play critical roles on improving human health. The modulating effect of astaxanthin on gut microbiota has been reported. However, little is known about the co-occurrence patterns among microbial taxa in response to astaxanthin. In this study, the gut microbial composition, co-occurrence patterns, and microbial correlations with physiological parameters in astaxanthin-fed normal and obese mice were studied. Astaxanthin altered the microbial composition and co-occurrence patterns in normal and obese mice. Furthermore, astaxanthin gave more profound impacts on microbiota in obesity when compared with normal mice. In group A (normal or obese mice supplemented with astaxanthin), the abundance of Acinetobacter was decreased, and Alistipes was increased by astaxanthin, which also occurred in the MA group (obese mice supplemented with astaxanthin). An operational taxonomic unit (OTU) (GreenGeneID# 4029632) assigned to the genus Bacteroides acted as a connector in the global network of A and MA groups. It may play critical roles in bridging intimate interactions between the host and other bacteria intervened by astaxanthin. Several modules correlated with physiological parameters were detected. For example, modules A12 and MA10 were significantly and negatively correlated with lipopolysaccharide (LPS) and fasting blood glucose (FBG) levels, respectively. A positive correlation was found between the node connectivity of the OTUs belonging to Clostridiaceae with LPS in obese mice, which indicated the role of Clostridiales as a potential pathological marker. Our findings provided a new interpretation of the role of astaxanthin in health and may contribute to further research on microbial community engineering.

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.

Effects of astaxanthin in animal models of obesity-associated diseases: A systematic review and meta-analysis

BACKGROUND AND AIM

Obesity is a major risk factor for several diseases, including metabolic syndrome (MetS), non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes (T2D). The use of natural products, such as astaxanthin (ASX), a potent antioxidant compound produced by the freshwater green microalga Haematococcus pluvialis, has gained particular interest to reduce oxidative stress and inflammation, and to improve redox status, often associated with obesity. A systematic review and meta-analysis was performed to comprehensively examine the effects of ASX in animal models of diet induced obesity-associated diseases in order to inform the design of future human clinical studies for ASX use as supplement or nutraceutical.

METHODS

Cinahl, Cochraine, MEDLINE, Scopus and Web of Science were searched for English-language manuscripts published between January 2000 and April 2020 using the following key words: astaxanthin, obesity, non-alcoholic fatty liver disease, diabetes mellitus type 2, NAFLD and metabolic.

RESULTS

Seventeen eligible articles, corresponding to 21 animal studies, were included in the final quantitative analysis. ASX, at different concentrations and administered for different length of time, induced a significant reduction in adipose tissue weight (P = 0.05) and systolic blood pressure (P < 0.0001) in control animals. In animal models of T2D, ASX significantly reduced serum glucose levels (P = 0.04); whereas it improved several disease biomarkers in the blood (e.g. cholesterol, triglycerides, ALT and AST, P < 0.10), and reduced liver (P = 0.0002) and body weight (P = 0.11), in animal models of NAFLD.

CONCLUSIONS

Supplementation of ASX in the diet has positive effects on symptoms associated with obesity related diseases in animals, by having lipid-lowering, hypo-insulin and hypoglycaemic capacity, protecting organs from oxidative stress and mitigating the immune system, as suggested in this review.

The Protein-Independent Role of Phosphate in the Progression of Chronic Kidney Disease

Several factors contribute to renal-function decline in CKD patients, and the role of phosphate content in the diet is still a matter of debate. This study aims to analyze the mechanism by which phosphate, independent of protein, is associated with the progression of CKD. Adult Munich-Wistar rats were submitted to 5/6 nephrectomy (Nx), fed with a low-protein diet, and divided into two groups. Only phosphate content (low phosphate, LoP, 0.2%; high phosphate, HiP, 0.95%) differentiated diets. After sixty days, biochemical parameters and kidney histology were analyzed. The HiP group presented worse renal function, with higher levels of PTH, FGF-23, and fractional excretion of phosphate. In the histological analysis of the kidney tissue, they also showed a higher percentage of interstitial fibrosis, expression of α-actin, PCNA, and renal infiltration by macrophages. The LoP group presented higher expression of beclin-1 in renal tubule cells, a marker of autophagic flux, when compared to the HiP group. Our findings highlight the action of phosphate in the induction of kidney interstitial inflammation and fibrosis, contributing to the progression of renal disease. A possible effect of phosphate on the dysregulation of the renal cell autophagy mechanism needs further investigation with clinical studies.

Astaxanthin Protects Dendritic Cells from Lipopolysaccharide-Induced Immune Dysfunction

Astaxanthin, originating from seafood, is a naturally occurring red carotenoid pigment. Previous studies have focused on its antioxidant properties; however, whether astaxanthin possesses a desired anti-inflammatory characteristic to regulate the dendritic cells (DCs) for sepsis therapy remains unknown. Here, we explored the effects of astaxanthin on the immune functions of murine DCs. Our results showed that astaxanthin reduced the expressions of LPS-induced inflammatory cytokines (TNF-α, IL-6, and IL-10) and phenotypic markers (MHCII, CD40, CD80, and CD86) by DCs. Moreover, astaxanthin promoted the endocytosis levels in LPS-treated DCs, and hindered the LPS-induced migration of DCs via downregulating CCR7 expression, and then abrogated allogeneic T cell proliferation. Furthermore, we found that astaxanthin inhibited the immune dysfunction of DCs induced by LPS via the activation of the HO-1/Nrf2 axis. Finally, astaxanthin with oral administration remarkably enhanced the survival rate of LPS-challenged mice. These data showed a new approach of astaxanthin for potential sepsis treatment through avoiding the immune dysfunction of DCs.

The roles and mechanisms of hypoxia in liver fibrosis

Liver fibrosis occurs in response to any etiology of chronic liver injury. Lack of appropriate clinical intervention will lead to liver cirrhosis or hepatocellular carcinoma (HCC), seriously affecting the quality of life of patients, but the current clinical treatments of liver fibrosis have not been developed yet. Recent studies have shown that hypoxia is a key factor promoting the progression of liver fibrosis. Hypoxia can cause liver fibrosis. Liver fibrosis can, in turn, profoundly further deepen the degree of hypoxia. Therefore, exploring the role of hypoxia in liver fibrosis will help to further understand the process of liver fibrosis, and provide the theoretical basis for its diagnosis and treatment, which is of great significance to avoid further deterioration of liver diseases and protect the life and health of patients. This review highlights the recent advances in cellular and molecular mechanisms of hypoxia in developments of liver fibrosis.

Shrimp Oil Extracted from Shrimp Processing By-Product Is a Rich Source of Omega-3 Fatty Acids and Astaxanthin-Esters, and Reveals Potential Anti-Adipogenic Effects in 3T3-L1 Adipocytes

The province of Newfoundland and Labrador, Canada, generates tons of shrimp processing by-product every year. Shrimp contains omega (n)-3 polyunsaturated fatty acids (PUFA) and astaxanthin (Astx), a potent antioxidant that exists in either free or esterified form (Astx-E). In this study, shrimp oil (SO) was extracted from the shrimp processing by-product using the Soxhlet method (hexane:acetone 2:3). The extracted SO was rich in phospholipids, n-3 PUFA, and Astx-E. The 3T3-L1 preadipocytes were differentiated to mature adipocytes in the presence or absence of various treatments for 8 days. The effects of SO were then investigated on fat accumulation, and the mRNA expression of genes involved in adipogenesis and lipogenesis in 3T3-L1 cells. The effects of fish oil (FO), in combination with Astx-E, on fat accumulation, and the mRNA expression of genes involved in adipogenesis and lipogenesis were also investigated. The SO decreased fat accumulation, compared to untreated cells, which coincided with lower mRNA expression of adipogenic and lipogenic genes. However, FO and FO + Astx-E increased fat accumulation, along with increased mRNA expression of adipogenic and lipogenic genes, and glucose transporter type 4 (Glut-4), compared to untreated cells. These findings have demonstrated that the SO is a rich source of n-3 PUFA and Astx-E, and has the potential to elicit anti-adipogenic effects. Moreover, the SO and FO appear to regulate adipogenesis and lipogenesis via independent pathways in 3T3-L1 cells.

Current innovations in nutraceuticals and functional foods for intervention of non-alcoholic fatty liver disease

As innovations in global agricultural production and food trading systems lead to major dietary shifts, high morbidity rates from non-alcoholic fatty liver disease (NAFLD), accompanied by elevated risk of lipid metabolism-related complications, has emerged as a growing problem worldwide. Treatment and prevention of NAFLD and chronic liver disease depends on the availability of safe, effective, and diverse therapeutic agents, the development of which is urgently needed. Supported by a growing body of evidence, considerable attention is now focused on interventional approaches that combines nutraceuticals and functional foods. In this review, we summarize the pathological progression of NAFLD and discuss the beneficial effects of nutraceuticals and the active ingredients in functional foods. We also describe the underlying mechanisms of these compounds in the intervention of NAFLD, including their effects on regulation of lipid homeostasis, activation of signaling pathways, and their role in gut microbial community dynamics and the gut-liver axis. In order to identify novel targets for treatment of lipid metabolism-related diseases, this work broadly explores the molecular mechanism linking nutraceuticals and functional foods, host physiology, and gut microbiota. Additionally, the limitations in existing knowledge and promising research areas for development of active interventions and treatments against NAFLD are discussed.

A Fundamental Role for Oxidants and Intracellular Calcium Signals in Alzheimer's Pathogenesis-And How a Comprehensive Antioxidant Strategy May Aid Prevention of This Disorder

Oxidative stress and increased cytoplasmic calcium are key mediators of the detrimental effects on neuronal function and survival in Alzheimer's disease (AD). Pathways whereby these perturbations arise, and then prevent dendritic spine formation, promote tau hyperphosphorylation, further amplify amyloid β generation, and induce neuronal apoptosis, are described. A comprehensive program of nutraceutical supplementation, comprised of the NADPH oxidase inhibitor phycocyanobilin, phase two inducers, the mitochondrial antioxidant astaxanthin, and the glutathione precursor N-acetylcysteine, may have important potential for antagonizing the toxic effects of amyloid β on neurons and thereby aiding prevention of AD. Moreover, nutraceutical antioxidant strategies may oppose the adverse impact of amyloid β oligomers on astrocyte clearance of glutamate, and on the ability of brain capillaries to export amyloid β monomers/oligomers from the brain. Antioxidants, docosahexaenoic acid (DHA), and vitamin D, have potential for suppressing microglial production of interleukin-1β, which potentiates the neurotoxicity of amyloid β. Epidemiology suggests that a health-promoting lifestyle, incorporating a prudent diet, regular vigorous exercise, and other feasible measures, can cut the high risk for AD among the elderly by up to 60%. Conceivably, complementing such lifestyle measures with long-term adherence to the sort of nutraceutical regimen outlined here may drive down risk for AD even further.

MiR-146a-5p targeting SMAD4 and TRAF6 inhibits adipogenensis through TGF-β and AKT/mTORC1 signal pathways in porcine intramuscular preadipocytes

BACKGROUND

Intramuscular fat (IMF) content is a vital parameter for assessing pork quality. Increasing evidence has shown that microRNAs (miRNAs) play an important role in regulating porcine IMF deposition. Here, a novel miRNA implicated in porcine IMF adipogenesis was found, and its effect and regulatory mechanism were further explored with respect to intramuscular preadipocyte proliferation and differentiation.

RESULTS

By porcine adipose tissue miRNA sequencing analysis, we found that miR-146a-5p is a potential regulator of porcine IMF adipogenesis. Further studies showed that miR-146a-5p mimics inhibited porcine intramuscular preadipocyte proliferation and differentiation, while the miR-146a-5p inhibitor promoted cell proliferation and adipogenic differentiation. Mechanistically, miR-146a-5p suppressed cell proliferation by directly targeting SMAD family member 4 (SMAD4) to attenuate TGF-β signaling. Moreover, miR-146a-5p inhibited the differentiation of intramuscular preadipocytes by targeting TNF receptor-associated factor 6 (TRAF6) to weaken the AKT/mTORC1 signaling downstream of the TRAF6 pathway.

CONCLUSIONS

MiR-146a-5p targets SMAD4 and TRAF6 to inhibit porcine intramuscular adipogenesis by attenuating TGF-β and AKT/mTORC1 signaling, respectively. These findings provide a novel miRNA biomarker for regulating intramuscular adipogenesis to promote pork quality.

Epigenetic immunomodulatory effect of eugenol and astaxanthin on doxorubicin cytotoxicity in hormonal positive breast Cancer cells

BACKGROUND

Hormonal receptor positive (HR+) breast cancer is the most commonly diagnosed molecular subtype of breast cancer; which showed good response to doxorubicin (DOX)-based chemotherapy. Eugenol (EUG) and astaxanthin (AST) are natural compounds with proved epigenetic and immunomodulatory effects in several cancer cell lines. This study has been initiated to investigate the molecular mechanism (s) whereby EUG and AST could enhance DOX cytotoxicity in MCF7 cells.

METHODS

Cytotoxic activity of DOX alone and combined with either 1 mM EUG or 40 μM AST was performed using sulphorhodamine-B assay in MCF7 cells. Global histones acetylation and some immunological markers were investigated using ELISA, western blotting and quantitative RT-PCR techniques. Functional assay of multidrug resistance was performed using rhodamine 123 and Hoechst 3342 dyes. Flow cytometry with annexin V and propidium iodide were used to assess the change in cell cycle and apoptosis along with the expression of some differentiation, apoptosis and autophagy proteins.

RESULTS

DOX alone resulted in concentration-dependent cytotoxicity with IC50 of 0.5 μM. Both EUG and AST significantly increased DOX cytotoxicity which is manifested as a significant decrease in DOX IC50 from 0.5 μM to 0.088 μM with EUG and to 0.06 μM with AST. Combinations of DOX with 1 mM EUG or 40 μM AST significantly increased the level of histones acetylation and histone acetyl transferase expression, while reduced the expression of aromatase and epidermal growth factor receptor (EGFR) when compared with 0.25 μM DOX alone. Also both combinations showed higher uptake of rhodamine but lower of Hoechst stains, along with increased the percentage of caspase 3, and decreased the expression of CK7 and LC3BI/II ratio. EUG combination induced IFγ but reduced TNFα causing shifting of cells from G2/M to S and G0/ G1 phases. Combination of DOX with EUG induced apoptosis through the higher BAX/ BCl2 ratio, while with AST was through the increase in caspase 8 expressions.

CONCLUSION

EUG and AST potentiated the anticancer activity of DOX through epigenetic histones acetylation along with the immunonomodulation of different apoptotic approaches in MCF7 cells.

Molecular mechanism of down-regulating adipogenic transcription factors in 3T3-L1 adipocyte cells by bioactive anti-adipogenic compounds

Obesity is growing at an alarming rate, which is characterized by increased adipose tissue. It increases the probability of many health complications, such as diabetes, arthritis, cardiac disease, and cancer. In modern society, with a growing population of obese patients, several individuals have increased insulin resistance. Herbal medicines are known as the oldest method of health care treatment for obesity-related secondary health issues. Several traditional medicinal plants and their effective phytoconstituents have shown anti-diabetic and anti-adipogenic activity. Adipose tissue is a major site for lipid accumulation as well as the whole-body insulin sensitivity region. 3T3-L1 cell line model can achieve adipogenesis. Adipocyte characteristics features such as expression of adipocyte markers and aggregation of lipids are chemically induced in the 3T3-L1 fibroblast cell line. Differentiation of 3T3-L1 is an efficient and convenient way to obtain adipocyte like cells in experimental studies. Peroxisome proliferation activated receptor γ (PPARγ) and Cytosine-Cytosine-Adenosine-Adenosine-Thymidine/Enhancer-binding protein α (CCAAT/Enhancer-binding protein α or C/EBPα) are considered to be regulating adipogenesis at the early stage, while adiponectin and fatty acid synthase (FAS) is responsible for the mature adipocyte formation. Excess accumulation of these adipose tissues and lipids leads to obesity. Thus, investigating adipose tissue development and the underlying molecular mechanism is important in the therapeutical approach. This review describes the cellular mechanism of 3T3-L1 fibroblast cells on potential anti-adipogenic herbal bioactive compounds.

Replacing fish oil and astaxanthin by microalgal sources produced different metabolic responses in juvenile rainbow trout fed 2 types of practical diets

Dietary fish oil supplementation provides n-3 long-chained polyunsaturated fatty acids for supporting fish growth and metabolism and enriching fillet with eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; c22:6n-3). Two experiments were performed as a 3 × 2 factorial arrangement of dietary treatments for 16 wk to determine effects and mechanisms of replacing 0%, 50%, and 100% fish oil with DHA-rich microalgae in combination with synthetic vs. microalgal source of astaxanthin in plant protein meal (PM)- or fishmeal (FM)- based diets for juvenile rainbow trout (Oncorhynchus mykiss). Fish (22 ± 0.26 g) were stocked at 17/tank and 3 tanks/diet. The 100% fish oil replacement impaired (P < 0.0001) growth performance, dietary protein and energy utilization, body indices, and tissue accumulation of DHA and EPA in both diet series. The impairments were associated (P < 0.05) with upregulation of hepatic gene expression related to growth (ghr1and igf1) and biosynthesis of DHA and EPA (fads6 and evol5) that was more dramatic in the FM than PM diet-fed fish, and more pronounced on tissue EPA than DHA concentrations. The source of astaxanthin exerted interaction effects with the fish oil replacement on several measures including muscle total cholesterol concentrations. In conclusion, replacing fish oil by the DHA-rich microalgae produced more negative metabolic responses than the substitution of synthetic astaxanthin by the microalgal source in juvenile rainbow trout fed 2 types of practical diets.

Dietary Supplementation of Astaxanthin Improved the Growth Performance, Antioxidant Ability and Immune Response of Juvenile Largemouth Bass (Micropterus salmoides) Fed High-Fat Diet

High-fat diet (HFD) usually induces oxidative stress and astaxanthin is regarded as an excellent anti-oxidant. An 8-week feeding trial was conducted to investigate the effects of dietary astaxanthin supplementation on growth performance, lipid metabolism, antioxidant ability, and immune response of juvenile largemouth bass (Micropterus salmoides) fed HFD. Four diets were formulated: the control diet (10.87% lipid, C), high-fat diet (18.08% lipid, HF), and HF diet supplemented with 75 and 150 mg kg^-1 astaxanthin (HFA1 and HFA2, respectively). Dietary supplementation of astaxanthin improved the growth of fish fed HFD, also decreased hepatosomatic index and intraperitoneal fat ratio of fish fed HFD, while having no effect on body fat. Malondialdehyde content and superoxide dismutase activity were increased in fish fed HFD, astaxanthin supplementation in HFD decreased the oxidative stress of fish. The supplementation of astaxanthin in HFD also reduced the mRNA levels of Caspase 3, Caspase 9, BAD, and IL15. These results suggested that dietary astaxanthin supplementation in HFD improved the growth performance, antioxidant ability and immune response of largemouth bass.

Potential of natural astaxanthin in alleviating the risk of cytokine storm in COVID-19

Host excessive inflammatory immune response to SARS-CoV-2 infection is thought to underpin the pathogenesis of COVID-19 associated severe pneumonitis and acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Once an immunological complication like cytokine storm occurs, anti-viral based monotherapy alone is not enough. Additional anti-inflammatory treatment is recommended. It must be noted that anti-inflammatory drugs such as JAK inhibitors, IL-6 inhibitors, TNF-α inhibitors, colchicine, etc., have been either suggested or are under trials for managing cytokine storm in COVID-19 infections. Natural astaxanthin (ASX) has a clinically proven safety profile and has antioxidant, anti-inflammatory, and immunomodulatory properties. There is evidence from preclinical studies that supports its preventive actions against ALI/ARDS. Moreover, ASX has a potent PPARs activity. Therefore, it is plausible to speculate that ASX could be considered as a potential adjunctive supplement. Here, we summarize the mounting evidence where ASX is shown to exert protective effect by regulating the expression of pro-inflammatory factors IL-1β, IL-6, IL-8 and TNF-α. We present reports where ASX is shown to prevent against oxidative damage and attenuate exacerbation of the inflammatory responses by regulating signaling pathways like NF-ĸB, NLRP3 and JAK/STAT. These evidences provide a rationale for considering natural astaxanthin as a therapeutic agent against inflammatory cytokine storm and associated risks in COVID-19 infection and this suggestion requires further validation with clinical studies.

Consumption of Spinach and Tomato Modifies Lipid Metabolism, Reducing Hepatic Steatosis in Rats

Non-alcoholic fatty liver disease (NAFLD) is currently a serious and growing clinical problem in developed and developing countries and is considered one of the most frequent chronic liver diseases in the world. The aim of this study was to evaluate the functionality of dietary carotenoids provided by tomato and spinach in the dietary treatment of steatosis. Twenty-two Sprague-Dawley rats with induced steatosis were grouped into three groups and fed standard diet (CD group) and two experimental diets supplemented with 12.75% (LC12.75 group) and 25.5% (HC25.5 group) of a mixture of spinach and tomato powder. Rats fed carotenoid-rich feeds showed an improvement in the plasma biomarkers of steatosis, with lower levels of glucose, total cholesterol, VLDL, TG, proteins, ALT and AST. Likewise, a decrease in oxidative stress was observed, with a significant reduction of malondialdehyde (MDA) in plasma (up to 54%), liver (up to 51.42%) and urine (up to 78.89%) (p < 0.05) and an increase in plasma antioxidant capacity (ORAC) (up to 73.41%) (p < 0.05). Furthermore, carotenoid-rich diets led to an accumulation of carotenoids in the liver and were inversely correlated with the content of total cholesterol and hepatic triglycerides, increasing the concentrations of MUFA and PUFA (up to 32.6% and 48%, respectively) (p < 0.05). The accumulation of carotenoids in the liver caused the modulation of genes involved in lipid metabolism, and we particularly observed an overexpression of ACOX1, APOA1 and NRIH2 (LXR) and the synthesis of the proteins. This study suggests that dietary carotenoids from spinach and tomato aid in the dietary management of steatosis by reversing steatosis biomarkers.

Absorbability of Astaxanthin Was Much Lower in Obese Mice Than in Normal Mice

Astaxanthin has been favored as a health food supplement by obese consumers. However, no detailed descriptions are available concerning the absorption of astaxanthin in obese individuals. In this study, we conducted acute and chronic feeding experiments in C57BL/6J mice to study the differences in astaxanthin absorption in normal and obese bodies. The obesity condition greatly decreased astaxanthin concentration in the blood and liver, its accumulation in tissues and organs, and the bioaccessibility. This may be related to the excessive intake of sucrose, fatty acids, and cholesterol, the increased gastrointestinal motility, and the disorder of gut microbiota in the obese body. Overall, our study showed that the obese body had a far less oral absorbability of astaxanthin than a normal body, and we suggest that the recommended or approved doses of astaxanthin can be properly increased for the obese body in the hope that astaxanthin will play a more active role in obese individuals.

Astaxanthin Inhibits p70 S6 Kinase 1 Activity to Sensitize Insulin Signaling

Astaxanthin (AST) is a carotenoid with therapeutic values on hyperglycemia and diabetic complications. The mechanisms of action of AST remain incompletely understood. p70 S6 kinase 1 (S6K1) is a serine/threonine kinase that phosphorylates insulin receptor substrate 1 (IRS-1)^S1101 and desensitizes the insulin receptor (IR). Our present study aims to determine if AST improves glucose metabolisms by targeting S6K1. Western blot analysis revealed that AST inhibited the phosphorylation of two S6K1 substrates, S6^S235/236 and IRS-1^S1101, but enhanced the phosphorylation of AKT^T308, AKT^S473, and S6K1^T389 by feedback activation of the phosphatidylinositol-3 (PI-3) kinase in 3T3-L1 adipocytes and L6 myotubes. In vitro kinase assays revealed that AST inhibited S6K1 activity with an IC₅₀ value of approximately 13.8 μM. AST increased insulin-induced IR tyrosine phosphorylation and IRS-1 binding to the p85 subunit of PI-3 kinase. Confocal microscopy revealed that AST increased the translocation of the glucose transporter 4 (GLUT4) to the plasma membrane in L6 cells. Glucose uptake assays using a fluorescent dye, 2-NBDG (2-N-(Nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose), revealed that AST increased glucose uptake in 3T3-L1 adipocytes and L6 myotubes under insulin resistance conditions. Our study identifies S6K1 as a previously unrecognized molecular target of AST and provides novel insights into the mechanisms of action of AST on IR sensitization.

Fermented mulberry (Morus alba) leaves suppress high fat diet-induced hepatic steatosis through amelioration of the inflammatory response and autophagy pathway

BACKGROUND

A novel extract of mulberry leaves fermented with Cordyceps militaris (EMfC) is reported to exert anti-obesity activity, although their molecular mechanism during hepatic steatosis has not verified.

METHODS

To investigate the role of inflammation and autophagy during the anti-hepatic steatosis effects of EMfC, we measured alterations in the key parameters for inflammatory response and autophagy pathway in liver tissues of the high fat diet (HFD) treated C57BL/6N mice after exposure to EMfC for 12 weeks.

RESULTS

Significant anti-hepatic steatosis effects, including decreased number of lipid droplets and expression of Klf2 mRNA, were detected in the liver of the HFD + EMfC treated group. The levels of mast cell infiltration, expression of two inflammatory mediators (iNOS and COX-2), and the MAPK signaling pathway were remarkably decreased in the liver of HFD + EMfC treated group as compared to the HFD + Vehicle treated group. Furthermore, a similar inhibitory effect was measured for the expression levels of pro-inflammatory cytokines, including IL-1β, IL-6, TNF-α and NF-κB. The expression level of members in the AKT/mTOR signaling pathway (a central regulator in autophagy) was recovered after treatment with EMfC, and autophagy-related proteins (Beclin and LC3-II) were remarkably decreased in the HFD + EMfC treated group compared to the HFD + Vehicle treated group. Moreover, the HFD + EMfC treated group showed decreased transcript levels of autophagy-regulated genes including Atg4b, Atg5, Atg7 and Atg12.

CONCLUSIONS

Taken together, findings of the present study provide novel evidences that the anti-hepatic steatosis of EMfC is tightly linked to the regulation of the inflammatory response and autophagy pathway in the liver tissue of HFD-induced obesity mice.

Effect of Astaxanthin on the Inhibition of Lipid Accumulation in 3T3-L1 Adipocytes via Modulation of Lipogenesis and Fatty Acid Transport Pathways

Obesity is defined as a condition of excessive fat tissue accumulation. It was the major factor most closely associated with lifestyle-related diseases. In the present study, we investigated the effect of astaxanthin on the inhibition of lipid accumulation in 3T3-L1 adipocytes. 3T3-L1 adipocytes were treated with 0–25 µg/mL of astaxanthin for 0–48 h. The result indicated that astaxanthin significantly decreased the oil Red O stained material (OROSM), intracellular triglyceride accumulation, and glycerol 3-phosphate dehydrogenase (GPDH) activity in 3T3-L1 adipocytes (p < 0.05). At the molecular level, astaxanthin significantly down-regulated the mRNA expression of peroxisome proliferator-activated receptor-γ (PPARγ) in 3T3-L1 adipocytes (p < 0.05). Moreover, target genes of PPARγ on the inhibition of lipogenesis, such as Acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), fatty acid binding protein (aP2), cluster of differentiation 36 (CD36), and lipoprotein lipase (LPL) in 3T3-L1 adipocytes were significantly down-regulated at a time-dependent manner (p < 0.05). These results suggested that astaxanthin efficiently suppressed lipid accumulation in 3T3-L1 adipocytes and its action is associated with the down-regulation of lipogenesis-related genes and the triglyceride accumulation in 3T3-L1 adipocytes. Therefore, astaxanthin can be developed as a potential nutraceutical ingredient for the prevention of obesity in a niche market.

Astaxanthin attenuates hepatic damage and mitochondrial dysfunction in non-alcoholic fatty liver disease by up-regulating the FGF21/PGC-1α pathway

BACKGROUND AND PURPOSE

Non-alcoholic fatty liver disease (NAFLD) is considered to be one of the most common chronic liver diseases across worldwide. Astaxanthin (Ax) is a carotenoid, and beneficial effects of astaxanthin, including anti-oxidative, anti-inflammatory, and anti-tumour activity, have been identified. The present study aimed to elucidate the protective effect of astaxanthin against NAFLD and its underlying mechanism.

EXPERIMENTAL APPROACH

Mice were fed either a high fat or chow diet, with or without astaxanthin, for up to 12 weeks. L02 cells were treated with free fatty acids combined with different doses of astaxanthin for 48 h. Histopathology, expression of lipid metabolism, inflammation, apoptosis, and fibrosis-related gene expression were assessed. And the function of mitochondria was also evaluated.

KEY RESULTS

The results indicated that astaxanthin attenuated HFD- and FFA-induced lipid accumulation and its associated oxidative stress, cell apoptosis, inflammation, and fibrosis both in vivo and in vitro. Astaxanthin up-regulated FGF21 and PGC-1α expression in damaged hepatocytes, which suggested an unrecognized mechanism of astaxanthin on ameliorating NAFLD.

CONCLUSION AND IMPLICATIONS

Astaxanthin attenuated hepatocyte damage and mitochondrial dysfunction in NAFLD by up-regulating FGF21/PGC-1α pathway. Our results suggest that astaxanthin may become a promising drug to treat or relieve NAFLD.

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.

Co-exposure to multi-walled carbon nanotube and lead ions aggravates hepatotoxicity of nonalcoholic fatty liver via inhibiting AMPK/PPARγ pathway

Multi-walled carbon nanotubes (MWCNTs) have been widely used in sewage disposal, water purification, and disinfection. Co-exposure to MWCNTs and heavy metal ions is common during water disposal. However, the hepatotoxicity of co-exposure to MWCNTs and lead ions for nonalcoholic fatty liver disease (NAFLD) subjects has not been investigated. NAFLD mice were fed intragastrically with MWCNTs and lead acetate (PbAc). Combined administration of MWCNTs and PbAc significantly damaged the liver function, and aggravated the nonalcoholic steatohepatitis phenotype as well as the hepatic fibrosis and steatosis in NAFLD mice. Furthermore, MWCNTs and PbAc significantly induced apoptosis in primary hepatocytes isolated from NAFLD mice. Combined administration of MWCNTs and PbAc also resulted in hepatic lipid peroxidation by inducing antioxidant defense system dysfunction, and significantly enhanced the expression levels of inflammatory cytokines in NAFLD mice livers. Meanwhile, combined administration of MWCNTs and PbAc may exert its hepatotoxicity in the NAFLD via inhibiting the adenosine 5'-monophosphate activated protein kinase (AMPK)/peroxisome proliferator-activated receptors γ (PPARγ) pathway. Taken together, we conclude that co-exposure to MWCNTs and PbAc can remarkably aggravate the hepatotoxicity in NAFLD mice via inhibiting the AMPK/PPARγ pathway. This study may provide a biosafety evaluation for the application of nanomaterials in wastewater treatment.

Astaxanthin in Liver Health and Disease: A Potential Therapeutic Agent

Astaxanthin is a carotenoid derived from oxygen-containing non-vitamin A sources and is mainly obtained from marine organisms. Studies have demonstrated that astaxanthin is a natural antioxidant product and it is widely used in the fields of medicine, health-care products and cosmetics. Studies have shown that astaxanthin has important preventive and therapeutic effects on liver fibrosis, non-alcoholic fatty liver, liver cancer, drug and ischemia-induced liver injury, and its mechanism is related to antioxidant and anti-inflammatory activities, and the regulation of multiple signaling pathways. In this review, we discuss the latest data on astaxanthin in the prevention and treatment of liver diseases. An understanding of the structure, source and mechanism of action of astaxanthin in the body would not only provide a theoretical basis for its clinical application but could also have important significance in screening and improving related compounds for the treatment of liver diseases.

Azelaic Acid Induces Mitochondrial Biogenesis in Skeletal Muscle by Activation of Olfactory Receptor 544

Mouse olfactory receptor 544 (Olfr544) is ectopically expressed in varied extra-nasal organs with tissue specific functions. Here, we investigated the functionality of Olfr544 in skeletal muscle cells and tissue. The expression of Olfr544 is confirmed by RT-PCR and qPCR in skeletal muscle cells and mouse skeletal muscle assessed by RT-PCR and qPCR. Olfr544 activation by its ligand, azelaic acid (AzA, 50 μM), induced mitochondrial biogenesis and autophagy in cultured skeletal myotubes by induction of cyclic adenosine monophosphate-response element binding protein (CREB)-peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α)-extracellular signal-regulated kinase-1/2 (ERK1/2) signaling axis. The silencing Olfr544 gene expression abrogated these effects of AzA in cultured myotubes. Similarly, in mice, the acute subcutaneous injection of AzA induced the CREB-PGC-1α-ERK1/2 pathways in mouse skeletal muscle, but these activations were negated in those of Olfr544 knockout mice. These demonstrate that the induction of mitochondrial biogenesis in skeletal muscle by AzA is Olfr544-dependent. Oral administration of AzA to high-fat-diet fed obese mice for 6 weeks increased mitochondrial DNA content in the skeletal muscle as well. Collectively, these findings demonstrate that Olfr544 activation by AzA regulates mitochondrial biogenesis in skeletal muscle. Intake of AzA or food containing AzA may help to improve skeletal muscle function.

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.

Adolescent exposure to environmental level of PCBs (Aroclor 1254) induces non-alcoholic fatty liver disease in male mice

Polychlorinated biphenyls (PCBs) are persistent organic pollutants found in various environmental media, and there is growing evidence that PCBs may contribute to the pathogenesis of non-alcoholic fatty liver disease (NAFLD). The purposes of this study were to investigate whether environmental level of Aroclor 1254 (a commercial mixture of PCBs) exposure to adolescent male mice could induce the development of NAFLD and the mechanisms involved. Twenty-one-day-old male C57BL/6 mice were exposed to Aroclor 1254 (0.5-500 μg/kg body weight) by oral gavage once every third day for 60 days. The results showed that exposure to Aroclor 1254 increased body weight and decreased the liver-somatic index in a dose-dependent manner. Aroclor 1254 administration increased lipid accumulation in the liver and induced the mRNA expression of genes associated with lipogenesis, including acetyl-CoA carboxylase 1 (Acc1), acetyl-CoA carboxylase 2 (Acc2) and fatty acid synthase (Fasn). Moreover, Aroclor 1254 decreased peroxisome proliferator-activated receptor alpha (PPARα) signaling and lipid oxidation. In addition, we found that Aroclor 1254 administration induced oxidative stress in mouse liver and elevated the protein level of cyclooxygenase 2 (COX-2), an inflammatory molecule, possibly via the endoplasmic reticulum (ER) stress inositol-requiring enzyme 1α-X-box-binding protein-1 (IRE1α-XBP1) pathway, but not the nuclear factor-κB (NF-κB) pathway. In summary, adolescent exposure to environmental level of PCBs stimulated oxidative stress, ER stress and the inflammatory response and caused NAFLD in male mice. This work provides new insight into the idea that adolescent exposure to environmental level of PCBs might induce the development of NAFLD under the regulation of ER stress in males.

Novel antioxidant astaxanthin-s-allyl cysteine biconjugate diminished oxidative stress and mitochondrial dysfunction to triumph diabetes in rat model

AIMS

The present study determines the effect of administration of novel antioxidant astaxanthin-s-allyl cysteine biconjugate (AST-SAC) against streptozotocin-induced diabetes mellitus (DM) in rats.

MAIN METHODS

AST-SAC (1 mg/kg/day) was treated against DM in rats for 45 days. The oxidative stress, antioxidants level, insulin secretion, activities of various carbohydrate metabolizing enzymes were studied. The glucose uptake in L6 myotubes was studied. In addition, in silico analysis of interaction of AST-SAC with proteins such as insulin receptor (IR) and 5'-adenosine monophosphate-activated protein kinase (AMPK) were carried out.

KEY FINDINGS

Administration of AST-SAC in DM rats has protected the mitochondrial function (decreased oxidative stress and normalized oxidative phosphorylation activities) and antioxidant capacity of the pancreas which has resulted in beta cells rejuvenation and insulin secretion restoration. AST-SAC decreased the alpha-glucosidases activities to bring glycemic control in DM rats. Due to these effects the glycoprotein components and lipids were restored to near normalcy in DM rats. AST-SAC protected the antioxidant status of liver, kidney and plasma; and curbed the progression of secondary complications of DM. AST-SAC treatment stimulated glucose uptake in L6 myotubes in in vitro. To support this observation, AST-SAC interacted with proteins such as IR and AMPK in silico.

SIGNIFICANCE

AST-SAC can be considered as "multi-target-directed ligand", that is, through these manifold effects, AST-SAC has been able to prevail over DM in rats.

Carotenoids and fatty liver disease: Current knowledge and research gaps

Carotenoids form an important part of the human diet, consumption of which has been associated with many health benefits. With the growing global burden of liver disease, increasing attention has been paid on the possible beneficial role that carotenoids may play in the liver. This review focuses on carotenoid actions in non-alcoholic fatty liver disease (NAFLD), and alcoholic liver disease (ALD). Indeed, many human studies have suggested an association between decreased circulating levels of carotenoids and increased incidence of NAFLD and ALD. The literature describing supplementation of individual carotenoids in rodent models of NAFLD and ALD is reviewed, with particular attention paid to β-carotene and lycopene, but also including β-cryptoxanthin, lutein, zeaxanthin, and astaxanthin. The effect of beta-carotene oxygenase 1 and 2 knock-out mice on hepatic lipid metabolism is also discussed. In general, there is evidence to suggest that carotenoids have beneficial effects in animal models of both NAFLD and ALD. Mechanistically, these benefits may occur via three possible modes of action: 1) improved hepatic antioxidative status broadly attributed to carotenoids in general, 2) the generation of vitamin A from β-carotene and β-cryptoxanthin, leading to improved hepatic retinoid signaling, and 3) the generation of apocarotenoid metabolites from β-carotene and lycopene, that may regulate hepatic signaling pathways. Gaps in our knowledge regarding carotenoid mechanisms of action in the liver are highlighted throughout, and the review ends by emphasizing the importance of dose effects, mode of delivery, and mechanism of action as important areas for further study. 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.

A pilot study on the effects of DHA/EPA-enriched phospholipids on aerobic and anaerobic exercises in mice

DHA/EPA-PL andl-carnitine had significant effects on aerobic exercise, while astaxanthin improved anaerobic exercise. The possible mechanism involved carbohydrate and lipid metabolism, mitochondrial respiratory chain and tricarboxylic acid cycle.

Anti-obesity potential of rare sugar d-psicose by regulating lipid metabolism in rats

d-Psicose is a new-generation sugar substitute with a low calorie count and can still offer the desirable sweetness. The objective of this study was to investigate the antiobesity potential of d-psicose and the possible mechanism using Wistar rats as the animal model. The animals were divided into five groups and supplemented with diets containing 5% of different carbohydrates, such as glucose, fructose, cellulose, d-psicose, and a control diet, for 4 weeks. After sacrifice, blood lipid profile, tissue morphology, and related genes participating in lipid metabolism were analyzed. The results indicated that the supplementation by d-psicose leads to minimum fat accumulation in rats when compared with the other carbohydrates. The blood lipid profile and antioxidative activity of the rat were also improved. d-Psicose can regulate lipid metabolism by increasing the lipid-metabolism-related enzymes such as SDH in serum and liver and HL in the liver. d-Psicose can prevent fat accumulation by suppressing the expression of lipogenesis-related gene ACCα and hepatic fatty acid uptake gene (FAS and SREBP-1c), while stimulating the expression for fatty-acid-oxidation-related gene including AMPK2α, HSL, and PPARα. In conclusion, d-psicose can be considered to be a healthy alternative to traditional sweeteners.

Supplementation with nitrate only modestly affects lipid and glucose metabolism in genetic and dietary-induced murine models of obesity

To gain a better understanding of how nitrate may affect carbohydrate and lipid metabolism, female wild-type mice were fed a high-fat, high-fructose diet supplemented with either 0, 400, or 800 mg nitrate/kg diet for 28 days. Additionally, obese female db/db mice were fed a 5% fat diet supplemented with the same levels and source of nitrate. Nitrate decreased the sodium-dependent uptake of glucose by ileal mucosa in wild-type mice. Moreover, nitrate significantly decreased triglyceride content and mRNA expression levels of Pparγ in liver and Glut4 in skeletal muscle. Oral glucose tolerance as well as plasma cholesterol, triglyceride, insulin, leptin, glucose and the activity of ALT did not significantly differ between experimental groups but was higher in db/db mice than in wild-type mice. Nitrate changed liver fatty acid composition and mRNA levels of Fads only slightly. Further hepatic genes encoding proteins involved in lipid and carbohydrate metabolism were not significantly different between the three groups. Biomarkers of inflammation and autophagy in the liver were not affected by the different dietary treatments. Overall, the present data suggest that short-term dietary supplementation with inorganic nitrate has only modest effects on carbohydrate and lipid metabolism in genetic and dietary-induced mouse models of obesity.

Astaxanthin Modulation of Signaling Pathways That Regulate Autophagy

Autophagy is a lysosomal pathway that degrades and recycles unused or dysfunctional cell components as well as toxic cytosolic materials. Basal autophagy favors cell survival. However, the aberrant regulation of autophagy can promote pathological conditions. The autophagy pathway is regulated by several cell-stress and cell-survival signaling pathways that can be targeted for the purpose of disease control. In experimental models of disease, the carotenoid astaxanthin has been shown to modulate autophagy by regulating signaling pathways, including the AMP-activated protein kinase (AMPK), cellular homolog of murine thymoma virus akt8 oncogene (Akt), and mitogen-activated protein kinase (MAPK), such as c-Jun N-terminal kinase (JNK) and p38. Astaxanthin is a promising therapeutic agent for the treatment of a wide variety of diseases by regulating autophagy.

Kaempferol reduces hepatic triglyceride accumulation by inhibiting Akt

In this paper, we studied the mechanism of the triglyceride (TG)-lowering effect of kaempferol in vitro and in vivo. Kaempferol showed LXR agonistic activities without inducing TGs or the expression of several lipogenic genes in cultured cells. A luciferase and qPCR analysis showed that kaempferol increased the transactivation of PPARα and PPARδ and stimulated gene expression associated with fatty acid oxidation and uptake in hepatocytes. More importantly, kaempferol inhibited protein kinase B (Akt) activity and suppressed SREBP-1 activation via multiple mechanisms, including through increasing Insig-2a expression, reducing SREBP-1 phosphorylation, and increasing GSK-3 phosphorylation. Collectively, these actions inhibited the SREBP-1 activation process. Furthermore, as an Akt/mTOR pathway inhibitor, kaempferol led to the induction of hepatic autophagy and resulted in a decrease in lipid droplet formation in the mouse liver. These findings demonstrate that kaempferol exerts its TG-lowering effect via Akt inhibition and activation of PPARα and PPARδ. PRACTICAL APPLICATIONS: Kaempferol is a major dietary flavonoid in various plant-based foods, and it is used as a valuable ingredient in functional foods, with numerous beneficial properties such as anticancer, antioxidant, and anti-atherosclerotic activities. Kaempferol exerts its TG-lowering effect via Akt inhibition and activation of PPARα and PPARδ. Currently, the number of people with hyperlipidemia is rapidly growing in both developed and developing societies; thus, we propose that kaempferol could be used for therapeutic interventions aimed at the treatment of these individuals.

Alpha-tocopherol in intravenous lipid emulsions imparts hepatic protection in a murine model of hepatosteatosis induced by the enteral administration of a parenteral nutrition solution

Intestinal failure-associated liver disease (IFALD) is a risk of parenteral nutrition (PN)-dependence. Intravenous soybean oil-based parenteral fat can exacerbate the risk of IFALD while intravenous fish oil can minimize its progression, yet the mechanisms by which soybean oil harms and fish oil protects the liver are uncertain. Properties that differentiate soybean and fish oils include α-tocopherol and phytosterol content. Soybean oil is rich in phytosterols and contains little α-tocopherol. Fish oil contains abundant α-tocopherol and little phytosterols. This study tested whether α-tocopherol confers hepatoprotective properties while phytosterols confer hepatotoxicity to intravenous fat emulsions. Utilizing emulsions formulated in the laboratory, a soybean oil emulsion (SO) failed to protect from hepatosteatosis in mice administered a PN solution enterally. An emulsion of soybean oil containing α-tocopherol (SO+AT) preserved normal hepatic architecture. A fish oil emulsion (FO) and an emulsion of fish oil containing phytosterols (FO+P) protected from steatosis in this model. Expression of hepatic acetyl CoA carboxylase (ACC) and peroxisome proliferator-activated receptor gamma (PPARγ), was increased in animals administered SO. ACC and PPARγ levels were comparable to chow-fed controls in animals receiving SO+AT, FO, and FO+P. This study suggests a hepatoprotective role for α-tocopherol in liver injury induced by the enteral administration of a parenteral nutrition solution. Phytosterols do not appear to compromise the hepatoprotective effects of fish oil.

Astaxanthin as a Peroxisome Proliferator-Activated Receptor (PPAR) Modulator: Its Therapeutic Implications

Peroxisome proliferator-activated receptors (PPARs) are part of the nuclear hormone receptors superfamily that plays a pivotal role in functions such as glucose and lipid homeostasis. Astaxanthin (ASX) is a lipid-soluble xanthophyll carotenoid synthesized by many microorganisms and various types of marine life that is known to possess antioxidant, anti-inflammatory, antidiabetic, anti-atherosclerotic, and anticancer activities. As such, it is a promising nutraceutical resource. ASX-mediated modulation of PPARs and its therapeutic implications in various pathophysiological conditions are described in this review. ASX primarily enhances the action of PPARα and suppresses that of PPARβ/δ and PPARγ, but it has also been confirmed that ASX displays the opposite effects on PPARs, depending on the cell context. Anti-inflammatory effects of ASX are mediated by PPARγ activation, which induces the expression of pro-inflammatory cytokines in macrophages and gastric epithelial cells. The PPARγ-agonistic effect of ASX treatment results in the inhibition of cellular growth and apoptosis in tumor cells. Simultaneous and differential regulation of PPARα and PPARγ activity by ASX has demonstrated a hepatoprotective effect, maintaining hepatic lipid homeostasis and preventing related hepatic problems. Considering additional therapeutic benefits of ASX such as anti-gastric, cardioprotective, immuno-modulatory, neuroprotective, retinoprotective, and osteogenic effects, more studies on the association between ASX-mediated PPAR regulation and its therapeutic outcomes in various pathophysiological conditions are needed to further elucidate the role of ASX as a novel nutraceutical PPAR modulator.

Ameliorative Effect of Spinach on Non-Alcoholic Fatty Liver Disease Induced in Rats by a High-Fat Diet

The purpose of this work was to evaluate the effect of dietary carotenoids from spinach on the inflammation and oxidative stress biomarkers, liver lipid profile, and liver transcriptomic and metabolomics profiles in Sprague–Dawley rats with steatosis induced by a high-fat diet. Two concentrations of spinach powder (2.5 and 5%) were used in two types of diet: high-fat (H) and standard (N). Although rats fed diet H showed an accumulation of fat in hepatocytes, they did not show differences in the values of adiponectin, tumor necrosis factor alpha (TNF-α), and oxygen radical absorption (ORAC) in plasma or of isoprostanes in urine compared with animals fed diet N. The consumption of spinach and the accumulation of α and β carotenes and lutein in the liver was inversely correlated with serum total cholesterol and glucose and the content of hepatic cholesterol, increasing monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA) and reducing cholesterol in the livers of rats fed diet H and spinach. In addition, changes in the expression of genes related to the fatty liver condition occurred, and the expression of genes involved in the metabolism of fatty acids and cholesterol increased, mainly through the overexpression of peroxisome proliferator activated receptors (PPARs). Related to liver metabolites, animals fed with diet H showed hypoaminoacidemia, mainly for the glucogenic aminoacids. Although no changes were observed in inflammation and oxidative stress biomarkers, the consumption of spinach modulated the lipid metabolism in liver, which must be taken into consideration during the dietary treatment of steatosis.

Autophagy in Human Health and Disease: Novel Therapeutic Opportunities

SIGNIFICANCE

In eukaryotes, autophagy represents a highly evolutionary conserved process, through which macromolecules and cytoplasmic material are degraded into lysosomes and recycled for biosynthetic or energetic purposes. Dysfunction of the autophagic process has been associated with the onset and development of many human chronic pathologies, such as cardiovascular, metabolic, and neurodegenerative diseases as well as cancer. Recent Advances: Currently, comprehensive research is being carried out to discover new therapeutic agents that are able to modulate the autophagic process in vivo. Recent evidence has shown that a large number of natural bioactive compounds are involved in the regulation of autophagy by modulating several transcriptional factors and signaling pathways.

CRITICAL ISSUES

Critical issues that deserve particular attention are the inadequate understanding of the complex role of autophagy in disease pathogenesis, the limited availability of therapeutic drugs, and the lack of clinical trials. In this context, the effects that natural bioactive compounds exert on autophagic modulation should be clearly highlighted, since they depend on the type and stage of the pathological conditions of diseases.

FUTURE DIRECTIONS

Research efforts should now focus on understanding the survival-supporting and death-promoting roles of autophagy, how natural compounds interact exactly with the autophagic targets so as to induce or inhibit autophagy and on the evaluation of their pharmacological effects in a more in-depth and mechanistic way. In addition, clinical studies on autophagy-inducing natural products are strongly encouraged, also to highlight some fundamental aspects, such as the dose, the duration, and the possible synergistic action of these compounds with conventional therapy.

Transcriptomic responses of Nile tilapia (Oreochromis niloticus) liver to environmental concentration of di(2-ethylhexyl)phthalate

Di-(2-ethylhexyl) phthalate (DEHP) is currently the most frequently detected phthalic acid esters (PAEs) compounds and can induce diverse toxicities on aquatic organisms. To understand the molecular responses of fish to DEHP, we performed transcriptomic profiles in liver of tilapia (Oreochromis niloticus) which were exposed to environmental concentration of DEHP. A total of 30.10 Mb and 30.16 Mb clean reads were retrieved from the control and DEHP treated libraries, respectively. De-novo assembly of all the clean reads obtained 58,585 unigenes. After comparing the two libraries, 2814 and 1790 genes were identified as significantly increased and depressed, respectively. Gene ontology (GO) classification system and Kyoto Encyclopedia of Genes and Genomes (KEGG) database analysis demonstrated that DEHP significantly disturbed the expression level of genes associated with immunity, endocrine and reproductive system, lipid metabolism and so on. Quantitative real-time PCR was performed to validate the results of RNA-sequencing (RNA-seq) analysis. The resulting data provide new insights for exploring the molecular basis of tilapia response to DEHP exposure.

High-fat diet overfeeding promotes nondetrimental liver steatosis in female mice

High-fat diet (HFD) feeding or leptin-deficient mice are extensively used as models resembling features of human nonalcoholic fatty liver disease (NAFLD). The concurrence of experimental factors as fat content and source or total caloric intake leads to prominent differences in the development of the hepatic steatosis and related disturbances. In this work, we characterized the hepatic lipid accumulation induced by HFD in wild-type (WT) and ob/ ob mice with the purpose of differentiating adaptations to HFD from those specific of increased overfeeding due to leptin deficiency-associated hyperphagia. Given that most published works have been done in male models, we used female mice with the aim of increasing the body of evidence regarding NAFLD in female subjects. HFD promoted liver lipid accumulation only in the hyperphagic strain. Nevertheless, a decrease of lipid droplet-associated cholesteryl ester (CE) in both WT and obese animals was observed. These changes were accompanied by an improvement in the profile of lipoproteins that transport cholesterol and liver function markers in plasma from ob/ ob mice and a lower hepatic index. Using primary hepatocytes from female mice, overaccumulation of CE induced by 0.4 mM oleic acid reversed in the presence of a specific Takeda G protein-coupled bile acid receptor agonist. Nevertheless, hepatocytes from male mice were not responsive. This study suggests that enterohepatic circulation of bile acids might be one of the factors that can affect sex dimorphism in NAFLD development, which underlines the importance of including female models in the NAFLD research field. NEW & NOTEWORTHY This work provides new insight into the use of high-fat diet as a model to induce nonalcoholic fatty liver disease in wild-type and ob/ ob female mice. We show that high-fat diet induces steatosis only in ob/ ob mice while, surprisingly, several health indicators improve. Noteworthy, experiments with primary hepatocytes from male and female mice show that they express Takeda G protein-coupled bile acid receptor and that it and bile acid enterohepatic circulation might be accountable for sex dimorphism in nonalcoholic fatty liver disease development.