L-Fucose-Rich Sulfated Glycans from Edible Brown Seaweed: A Promising Functional Food for Obesity and Energy Expenditure Improvement.

The global obesity epidemic, exacerbated by the sedentary lifestyle fostered by the COVID-19 pandemic, presents a growing socioeconomic burden due to decreased physical activity and increased morbidity. Current obesity treatments show promise, but they often come with expensive medications, frequent injections, and potential side effects, with limited success in improving obesity through increased energy expenditure. This study explores the potential of a refined sulfated polysaccharide (SPSL), derived from the brown seaweed Scytosiphon lomentaria (SL), as a safe and effective anti-obesity treatment by promoting energy expenditure. Chemical characterization revealed that SPSL, rich in sulfate and L-fucose content, comprises nine distinct sulfated glycan structures. In vitro analysis demonstrated potent anti-lipogenic properties in adipocytes, mediated by the downregulation of key adipogenic modulators, including 5' adenosine monophosphate-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor γ (PPARγ) pathways. Inhibiting AMPK attenuated the anti-adipogenic effects of SPSL, confirming its involvement in the mechanism of action. Furthermore, in vivo studies using zebrafish models showed that SPSL increased energy expenditure and reduced lipid accumulation. These findings collectively highlight the therapeutic potential of SPSL as a functional food ingredient for mitigating obesity-related metabolic dysregulation by promoting energy expenditure. Further mechanistic and preclinical investigations are warranted to fully elucidate its mode of action and evaluate its efficacy in obesity management, potentially offering a novel, natural therapeutic avenue for this global health concern.

Alcalase-Assisted Mytilus edulis Hydrolysate: A Nutritional Approach for Recovery from Muscle Atrophy.

Muscle atrophy is a complex physiological condition caused by a variety of reasons, including muscle disuse, aging, malnutrition, chronic diseases, immobilization, and hormonal imbalance. Beyond its effect on physical appearance, this condition significantly reduces the quality of human life, thus warranting the development of preventive strategies. Although exercising is effective in managing this condition, it is applicable only for individuals who can engage in physical activities and are not bedridden. A combination of exercise and nutritional supplementation has emerged as a more advantageous approach. Here, we evaluated the effects of enzyme-assisted hydrolysates of Mytilus edulis prepared using Protamex (PMH), Alcalase (AMH), or Flavourzyme (FMH) in protecting against muscle atrophy in a dexamethasone (Dex)-induced muscular atrophy model in vitro and in vitro. Alcalase-assisted M. edulis hydrolysate (AMH) was the most efficient among the tested treatments and resulted in higher protein recovery (57.06 ± 0.42%) and abundant amino acid composition (43,158 mg/100 g; 43.16%). AMH treatment also escalated the proliferation of C2C12 cells while increasing the total number of nuclei, myotube coverage, and myotube diameter. These results were corroborated by a successful reduction in the levels of proteins responsible for muscle atrophy, including E3 ubiquitin ligases, and an increase in the expression of proteins associated with muscle hypertrophy, including myogenin and MyHC. These results were further solidified by the successful enhancement of locomotor ability and body weight in zebrafish following AMH treatment. Thus, these findings highlight the potential of AMH in recovery from muscle atrophy.

The Influence of Solvent Choice on the Extraction of Bioactive Compounds from Asteraceae: A Comparative Review.

While the potential of Asteraceae plants as herbal remedies has been globally recognized, their widespread application in the food, cosmetic, and pharmaceutical industries requires a deeper understanding of how extraction methods influence bioactive compound yields and functionalities. Previous research has primarily focused on the physiological activities or chemical compositions of individual Asteraceae species, often overlooking the critical role of solvent selection in optimizing extraction. Additionally, the remarkable physiological activities observed in these plants have spurred a growing number of clinical trials, aiming to validate their efficacy and safety for potential therapeutic and commercial applications. This work aims to bridge these knowledge gaps by providing an integrated analysis of extraction techniques, the diverse range of bioactive compounds present in Asteraceae, and the influence of solvent choice on isolating these valuable substances. By elucidating the interplay between extraction methods, solvent properties, and bioactivity, we underscore the promising potential of Asteraceae plants and highlight the importance of continued research, including clinical trials, to fully unlock their potential in the food, cosmetic, and pharmaceutical sectors.

A Combination Study of Pre- and Clinical Trial: Seaweed Consumption Reduces Aging-Associated Muscle Loss!

Seaweed consumption in Asian food cultures may benefit longevity and age-related conditions like sarcopenia with aging. However, sarcopenia lacks a definitive treatment, and pharmaceutical options have limitations in efficacy and safety. Recent studies on aging female mice found that Ishige okamurae (IO), a brown algae, and its active compound diphloroethohydroxycarmalol improved sarcopenia. Further research is needed to understand the effects of seaweed consumption on sarcopenia in humans. This clinical trial divided participants into a test group (receiving 500 mg/kg IO supplementation, mean±SD; age 62.73±7.18 years, n=40) and a control group (age 63.10±7.06 years, n=40). Hazard analysis assessed vital signs and muscle strength improvement during the trial. Additionally, 12-month-old mice were oral-fed IO at different doses (50, 100, 200 mg/kg) for 6-weeks. Aging and muscle-wasting related markers were evaluated, including grip strength, body weight and compositions, serum-parameters, and molecular-changes. The clinical trial found no significant changes in toxicity-parameters between the groups (p<0.05) after 12-weeks of IO supplementation. The IO group exhibited a remarkable increase in lower-limb quadriceps muscle-strength compared to the control (p=0.002). Furthermore, IO treatment improved age-related decline in quadriceps strength in the subgroup; under 61-years-old (p=0.004), without significant differences in foot-dominancy between groups (p=0.171). In 12-month-old male mice, IO administration improved age-related deficiencies in grip strength (p>0.0001) and testosterone (p=0.0001). Muscular regeneration parameters, such as lean-mass (p>0.0001), inhibition of proteolysis (measured by changes in myogenin and atrogin-1 protein expressions), cross-sectional myofiber area (p>0.0001), number of satellite cells (p=0.0001), and increased mitochondrial oxidative phosphorylation complexes in muscle tissue indicative of mitochondrial biogenesis, were also improved by IO administration. This trial is the first to explore the positive association between consuming brown-algae IO and age-related decreases in muscle strength. IO treatment helps maintain muscle mass and delays muscle wasting during aging, suggesting it as a potent nutritional strategy to protect against aging-associated sarcopenia.

In Vitro and In Vivo Protective Effects of Agaro-Oligosaccharides against Hydrogen Peroxide-Stimulated Oxidative Stress.

In our previous research, we investigated the anti-inflammatory activity of the agaro-oligosaccharides prepared from the agar of Gracilaria lemaneiformis (AO). In the present study, in order to further explore the bioactivities of AO, the antioxidant activity of AO was investigated in vitro in Vero cells and in vivo in zebrafish. AO scavenged alkyl, 1,1-diphenyl-2-picrylhydrazyl, and hydroxyl radicals at the IC50 value of 4.86 ± 0.13, 3.02 ± 0.44, and 1.33 ± 0.05 mg/mL, respectively. AO significantly suppressed hydrogen peroxide (H2O2)-stimulated oxidative damage by improving cell viability. This happened via suppressing apoptosis by scavenging intracellular reactive oxygen species (ROS). Furthermore, the in vivo results displayed that AO protected zebrafish against H2O2-stimulated oxidative damage by reducing the levels of intracellular ROS, cell death, and lipid peroxidation in a dose-dependent manner. These results indicate that AO effectively alleviated in vitro and in vivo oxidative damage stimulated by H2O2, and suggest the potential of AO in the cosmetic and functional food industries.

Antioxidant and anti-photoaging effects of a fucoidan isolated from Turbinaria ornata.

Fucoidans isolated from brown seaweeds are potential ingredients in the cosmetic industry. In our preosvious study, a fucoidan was isolated from the brown seaweed Turbinaria ornata (TO-F10) and the anti-inflammatory effect of TO-F10 was evaluated. In order to further explore the potential of TO-F10 in cosmetics, in the present study, antioxidant and photoprotective effects of TO-F10 were investigated. TO-F10 remarkably protected Vero cells against AAPH-stimulated cell death by reducing apoptosis via scavenging intracellular reactive oxygen species (ROS). In addition, TO-F10 increased the survival rate of AAPH-treated zebrafish by suppressing oxidative stress displayed in reducing the levels of ROS, cell death, and lipid peroxidation. Furthermore, TO-F10 effectively attenuated UVB-induced in vitro and in vivo photodamage. TO-F10 increased the viability of UVB-irradiated human keratinocytes via suppressing apoptosis by reducing the intracellular ROS level. Besides, TO-F10 effectively attenuated in vivo photodamage stimulated by UVB irradiation via inhibiting oxidative stress and inflammatory response in zebrafish. These results demonstrate that TO-F10 possesses in vitro and in vivo antioxidant and photoprotective effects, and suggest TO-F10 is a potential ingredient in the cosmetic industry.

Protective Effect of Sargassum fusiforme Fucoidan against Ethanol-Induced Oxidative Damage in In Vitro and In Vivo Models.

Our previous studies have evaluated the bioactivities of a fucoidan isolated from Sargassum fusiforme (SF-F). To further investigate the health benefit of SF-F, in the present study, the protective effect of SF-F against ethanol (EtOH)-induced oxidative damage has been evaluated in in vitro and in vivo models. SF-F effectively improved the viability of EtOH-treated Chang liver cells by suppressing apoptosis. In addition, the in vivo test results indicate that SF-F significantly and dose-dependently increased the survival rate of zebrafish treated with EtOH. Further research results show that this action works through decreasing cell death via reduced lipid peroxidation by scavenging intracellular reactive oxygen species in EtOH-stimulated zebrafish. These results indicate that SF-F effectively protected Chang liver cells and zebrafish against EtOH-induced oxidative damage and suggest the potential of SF-F to be used as an ingredient in the functional food industry.

Exploring the Potential of Olive Flounder Processing By-Products as a Source of Functional Ingredients for Muscle Enhancement.

Olive flounder (OF) is a widely aqua-cultivated and recognized socioeconomic resource in Korea. However, more than 50% of by-products are generated when processing one OF, and there is no proper way to utilize them. With rising awareness and interest in eco-friendly bio-materialization recycling, this research investigates the potential of enzymatic hydrolysis of OF by-products (OFB) to produce functional ingredients. Various enzymatic hydrolysates of OFB (OFBEs) were generated using 11 commercial enzymes. Among them, Prozyme 2000P-assisted OFBE (OFBP) exhibited the highest protein content and yield, as well as low molecularization. The muscle regenerative potential of OFBEs was evaluated using C2C12 myoblasts, revealing that OFBP positively regulated myoblast differentiation. In an in vitro Dex-induced myotube atrophy model, OFBP protected against muscle atrophy and restored myotube differentiation and Dex-induced reactive oxygen species (ROS) production. Furthermore, zebrafish treated with OFBEs showed improved locomotor activity and body weight, with OFBP exhibiting outstanding restoration in the Dex-induced muscle atrophy zebrafish in vivo model. In conclusion, OFBEs, particularly OFBP, produce hydrolysates with enhanced physiological usability and muscle regenerative potential. Further research on its industrial application and mechanistic insights is needed to realize its potential as a high-quality protein food ingredient derived from OF processing by-products.

Cosmeceutical Effects of Ishige okamurae Celluclast Extract.

Sulfated polysaccharides extracted from brown algae are unique algal polysaccharides and potential ingredients in the cosmeceutical, functional food, and pharmaceutical industries. Therefore, the present study evaluated the cosmeceutical effects, including antioxidant, anti-wrinkle, anti-inflammation, and photoprotective activities, of Ishige okamurae Celluclast extract (IOC). The IOC was abundant in sulfated polysaccharides (48.47%), polysaccharides (44.33%), and fucose (43.50%). Moreover, the IOC effectively scavenged free radicals, and its anti-inflammatory properties were confirmed in lipopolysaccharide-induced RAW 264.7 macrophages; therefore, the IOC may produce auxiliary effects by inhibiting reactive oxygen species (ROS). In vitro (Vero cells) and in vivo (zebrafish) studies further confirmed that the IOC produced a protective effect against hydrogen-peroxide-induced oxidative stress in a dose-dependent manner. In addition, the IOC suppressed intracellular ROS and apoptosis and enhanced HO-1 and SOD-1 expression through transcriptional activation of Nrf2 and downregulation of Keap1 in HaCaT cells. Furthermore, the IOC exhibited a potent protective effect against ultraviolet-B-induced skin damage and photoaging. In conclusion, the IOC possesses antioxidant, anti-inflammatory, and photoprotective activities, and can, therefore, be utilized in the cosmeceutical and functional food industries.

Detrimental impact of fine dust on zebrafish: Investigating a protective agent against ocular-damage using in vitro and in vivo models.

Pollution caused by fine dust is becoming a global problem in the aquatic environment. Many studies have investigated the hazards that fine dust may pose to terrestrial organisms; however, information on the effects on aquatic environments remain limited. In this study, the physicochemical characteristics of the fine dust associated with the captured powder or liquid state were compared using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Raw fine dust (RFD), in the captured powder state, was suspended in water (SFD), and the elemental composition, morphology, and size distribution of both were analyzed. Zebrafish were used as a model to study the effects of SFD-exposure on aquatic organisms. A fatal malformation was observed in the integuments of zebrafish exposed to SFD, specifically in the exterior and interior eye tissues. Furthermore, the exposure of SFD to Tg (flk; EGFP) zebrafish remarkably increased ocular vessel diameter expansion along with blood flow velocity. Regarding vessel diameter expansion, EA.hy926 cells exposed to SFD were adversely affected, with a significant increase in cell migration and capillary-like structure formation, which are angiogenic markers. The SFD-induced angiogenesis in vitro and in vivo was dramatically restored to normal via α/ß-adenosine isolated from the anti-angiogenic brown algae Ishige okamurae extract. Taken together, the current study presents solid evidence of the altered physicochemical characteristics of SFD compared to RFD, and the detrimental impact of SFD in an aquatic in vivo zebrafish model. In addition, the protective effect of α/ß-adenosine, a marine natural product, on SFD-induced angiogenesis suggests that it can be used as an agent to reduce the adverse effects of SFD on aquatic animals.

Reversibility of sarcopenia by Ishige okamurae and its active derivative diphloroethohydroxycarmalol in female aging mice.

With the rapid increase in the elderly population worldwide, the number of people with sarcopenia has also increased significantly, and this disease is emerging as a medical and social issue. The development of pharmaceutics targeting sarcopenia is limited owing to the occurrence of side effects, and exercise therapy also has a limited scope of application. Therefore, it is necessary to develop safe and biocompatible agents to treat age-related sarcopenia. Ishige okamurae (IO), an edible brown alga, and its active substance, diphloroethohydroxycarmalol (DPHC), have been reported to have various physiological functions, including skeletal muscle regeneration ability. However, this effect has not been verified in an in vivo aging model. As an aging model, the oral IO extracts and DPHC supplemented 14-month-old female C57BL/6J mice were compared to the young group in this study; the mice model showed a substantial restoration of physical exercise ability with the imbalance of famine hormone and senescence-associated secretary phenotypes compared with those in young mice. Regarding the lean mass increase in aging mice following IO extract and DPHC administration, the muscular characteristics and molecular alterations in the gastrocnemius and soleus muscles, which are sensitive to the damage that occurs during the aging process, were significantly improved. Collectively, the current study reveals that the natural agent IO extract and its derivative DPHC can reverse sarcopenia that occurs during the process of aging by improving the imbalance of muscle regeneration in vivo.

Vernicia fordii (Hemsl.) Airy Shaw extract stimulates insulin secretion in pancreatic ß-cells and improves insulin sensitivity in diabetic mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Vernicia fordii (Hemsl.) Airy Shaw (V. fordii) is also known as the tung tree and its leaves and fruit are used as an oriental treatment for dyspepsia, edema, and skin diseases, which are known as diabetic complications. AIM OF THE STUDY: In this study, we aimed to investigate the methanolic extract (VF5) of the leaves of V. fordii as an insulin secretagogue and its probable mechanism and verify the effect in HFD-fed mice. MATERIALS AND METHODS: The insulin secretagogue activity of different doses of VF5 (0.1, 0.3 and 1.0 µg/ml) was assessed using in vitro insulin secretion assay and confirmed the anti-diabetic effect in mice fed HFD for 4 weeks with different doses of VF5 (10, 20 and 50 mg/kg oral) for another 6 weeks. Glbenclamide (30 mg/kg, oral) was used as positive control drug. The possible mechanisms were evaluated by using Gö6983 (10 µM), U73122 (10 µM) and nifedipine (10 µM). The major constituents of VF5 were analyzed by UPLC-QToF-MS and 1H and 13C NMR spectroscopy. RESULTS: UPLC-QToF-MS and NMR spectroscopy analysis indicated that one of the main active components of VF5 was tigliane-diterpene esters. VF5 functioned as an insulin secretagogue and enhanced mitochondria respiration and insulin homeostasis. We confirmed that VF5 preserved the ß-cell and reduced the ß-cell expansion which caused by metabolic stress under HFD. The antidiabetic role of VF5 in HFD fed mice was assessed by glucose tolerance test (GTT) and insulin tolerance test (ITT), fasting plasma insulin level, fasting blood glucose level, AKT signal in peripheral tissue in the absence of toxic effects. Mechanistically, insulinotropic effect of VF5 was mediated by activation of PKCα via intracellular Ca2+ influx and enhanced mitochondria function. CONCLUSION: VF5 exhibits potent insulin secretagogue function and improves insulin sensitivity and protection of pancreatic ß-cells from metabolic stress without toxicity. Taken together, our study suggests that VF5 could be potentially used for treating diabetes and metabolic diseases through improving ß-cell function.

Hepatic MIR20B promotes nonalcoholic fatty liver disease by suppressing PPARA.

Background: Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive lipid accumulation and imbalances in lipid metabolism in the liver. Although nuclear receptors (NRs) play a crucial role in hepatic lipid metabolism, the underlying mechanisms of NR regulation in NAFLD remain largely unclear. Methods: Using network analysis and RNA-seq to determine the correlation between NRs and microRNA in human NAFLD patients, we revealed that MIR20B specifically targets PPARA. MIR20B mimic and anti-MIR20B were administered to human HepG2 and Huh-7 cells and mouse primary hepatocytes as well as high-fat diet (HFD)- or methionine-deficient diet (MCD)-fed mice to verify the specific function of MIR20B in NAFLD. We tested the inhibition of the therapeutic effect of a PPARα agonist, fenofibrate, by Mir20b and the synergic effect of combination of fenofibrate with anti-Mir20b in NAFLD mouse model. Results: We revealed that MIR20B specifically targets PPARA through miRNA regulatory network analysis of nuclear receptor genes in NAFLD. The expression of MIR20B was upregulated in free fatty acid (FA)-treated hepatocytes and the livers of both obesity-induced mice and NAFLD patients. Overexpression of MIR20B significantly increased hepatic lipid accumulation and triglyceride levels. Furthermore, MIR20B significantly reduced FA oxidation and mitochondrial biogenesis by targeting PPARA. In Mir20b-introduced mice, the effect of fenofibrate to ameliorate hepatic steatosis was significantly suppressed. Finally, inhibition of Mir20b significantly increased FA oxidation and uptake, resulting in improved insulin sensitivity and a decrease in NAFLD progression. Moreover, combination of fenofibrate and anti-Mir20b exhibited the synergic effect on improvement of NAFLD in MCD-fed mice. Conclusions: Taken together, our results demonstrate that the novel MIR20B targets PPARA, plays a significant role in hepatic lipid metabolism, and present an opportunity for the development of novel therapeutics for NAFLD. Funding: This research was funded by Korea Mouse Phenotyping Project (2016M3A9D5A01952411), the National Research Foundation of Korea (NRF) grant funded by the Korea government (2020R1F1A1061267, 2018R1A5A1024340, NRF-2021R1I1A2041463, 2020R1I1A1A01074940, 2016M3C9A394589324), and the Future-leading Project Research Fund (1.210034.01) of UNIST.

Anti-Obesity Effects of Grateloupia elliptica, a Red Seaweed, in Mice with High-Fat Diet-Induced Obesity via Suppression of Adipogenic Factors in White Adipose Tissue and Increased Thermogenic Factors in Brown Adipose Tissue.

Obesity is a serious metabolic syndrome characterized by high levels of cholesterol, lipids in the blood, and intracellular fat accumulation in adipose tissues. It is known that the suppression of adipogenic protein expression is an effective approach for the treatment of obesity, and regulates fatty acid storage and transportation in adipose tissues. The 60% ethanol extract of Grateloupia elliptica (GEE), a red seaweed from Jeju Island in Korea, was shown to exert anti-adipogenic activity in 3T3-L1 cells and in mice with high-fat diet (HFD)-induced obesity. GEE inhibited intracellular lipid accumulation in 3T3-L1 cells, and significantly reduced expression of adipogenic proteins. In vivo experiments indicated a significant reduction in body weight, as well as white adipose tissue (WAT) weight, including fatty liver, serum triglycerides, total cholesterol, and leptin contents. The expression of the adipogenic proteins, SREBP-1 and PPAR-γ, was significantly decreased by GEE, and the expression of the metabolic regulator protein was increased in WAT. The potential of GEE was shown in WAT, with the downregulation of PPAR-γ and C/EBP-α mRNA; in contrast, in brown adipose tissue (BAT), the thermogenic proteins were increased. Collectively, these research findings suggest the potential of GEE as an effective candidate for the treatment of obesity-related issues via functional foods or pharmaceutical agents.

PPM1A Controls Diabetic Gene Programming through Directly Dephosphorylating PPARγ at Ser273.

Peroxisome proliferator-activated receptor γ (PPARγ) is a master regulator of adipose tissue biology. In obesity, phosphorylation of PPARγ at Ser273 (pSer273) by cyclin-dependent kinase 5 (CDK5)/extracellular signal-regulated kinase (ERK) orchestrates diabetic gene reprogramming via dysregulation of specific gene expression. Although many recent studies have focused on the development of non-classical agonist drugs that inhibit the phosphorylation of PPARγ at Ser273, the molecular mechanism of PPARγ dephosphorylation at Ser273 is not well characterized. Here, we report that protein phosphatase Mg2+/Mn2+-dependent 1A (PPM1A) is a novel PPARγ phosphatase that directly dephosphorylates Ser273 and restores diabetic gene expression which is dysregulated by pSer273. The expression of PPM1A significantly decreases in two models of insulin resistance: diet-induced obese (DIO) mice and db/db mice, in which it negatively correlates with pSer273. Transcriptomic analysis using microarray and genotype-tissue expression (GTEx) data in humans shows positive correlations between PPM1A and most of the genes that are dysregulated by pSer273. These findings suggest that PPM1A dephosphorylates PPARγ at Ser273 and represents a potential target for the treatment of obesity-linked metabolic disorders.

Anti-obesity effects of red seaweed, Plocamium telfairiae, in C57BL/6 mice fed a high-fat diet.

This study aimed to demonstrate the anti-obesity effect of Plocamium telfairiae (PT), a red seaweed. Different percentages of ethanol (0%, 20%, 40%, 60%, 80%, and 100%) were used for the preparation of PT extract. Furthermore, 3T3-L1 cells were used to determine the percentage of ethanol for optimal anti-adipogenesis of PT, and the anti-obesity properties of the optimized extract of PT (PTE) (40%) was assessed in obese mice. The results indicate that 40% ethanol extract (40 PTE) significantly decreased fat accumulation and suppressed the expression of major adipogenesis factors such as peroxisome proliferator-activated receptor-γ (PPAR-γ), sterol regulatory element-binding protein 1 (SREBP-1), CCAAT/enhancer-binding protein (C/EBP)-α, and phosphorylated ACC (pACC) in 3T3-L1 cells. Furthermore, in the high-fat diet-induced obese mice, 40 PTE significantly reduced the weights of white adipose tissue, as well as the levels of triglyceride, total cholesterol, adiponectin, and insulin in the serum. Liver histopathology showed that steatosis decreased in all the PTE treatment groups. The adipogenesis-related proteins, PPAR-γ and SREBP-1, were also significantly decreased in PTE treatment groups. Additionally, 40 PTE increased mRNA expression of mitochondrial uncoupling proteins (UCP)-1 and UCP-3 in brown adipose tissue. These findings provide evidence that 40 PTE can alleviate lipid droplet accumulation in 3T3-L1 adipocytes and obese C57BL/6 mice, indicating that PTE has strong anti-obesity effects and could be used as a therapeutic agent or a component of pharmaceutical drugs and functional foods.

Flightless-1 inhibits ER stress-induced apoptosis in colorectal cancer cells by regulating Ca2+ homeostasis.

The endoplasmic reticulum (ER) stress response is an adaptive mechanism that is activated upon disruption of ER homeostasis and protects the cells against certain harmful environmental stimuli. However, critical and prolonged cell stress triggers cell death. In this study, we demonstrate that Flightless-1 (FliI) regulates ER stress-induced apoptosis in colon cancer cells by modulating Ca2+ homeostasis. FliI was highly expressed in both colon cell lines and colorectal cancer mouse models. In a mouse xenograft model using CT26 mouse colorectal cancer cells, tumor formation was slowed due to elevated levels of apoptosis in FliI-knockdown (FliI-KD) cells. FliI-KD cells treated with ER stress inducers, thapsigargin (TG), and tunicamycin exhibited activation of the unfolded protein response (UPR) and induction of UPR-related gene expression, which eventually triggered apoptosis. FliI-KD increased the intracellular Ca2+ concentration, and this upregulation was caused by accelerated ER-to-cytosolic efflux of Ca2+. The increase in intracellular Ca2+ concentration was significantly blocked by dantrolene and tetracaine, inhibitors of ryanodine receptors (RyRs). Dantrolene inhibited TG-induced ER stress and decreased the rate of apoptosis in FliI-KD CT26 cells. Finally, we found that knockdown of FliI decreased the levels of sorcin and ER Ca2+ and that TG-induced ER stress was recovered by overexpression of sorcin in FliI-KD cells. Taken together, these results suggest that FliI regulates sorcin expression, which modulates Ca2+ homeostasis in the ER through RyRs. Our findings reveal a novel mechanism by which FliI influences Ca2+ homeostasis and cell survival during ER stress.