HNF4α is required for Tkfc promoter activation by ChREBP.

Triokinase/FMN cyclase (Tkfc) is involved in fructose metabolism and is responsible for the phosphorylation of glyceraldehyde to glyceraldehyde-3-phosphate. In this study, we show that refeeding induced hepatic expression of Tkfc in mice. Luciferase reporter gene assays using the Tkfc promoter revealed the existence of two hepatocyte nuclear factor 4α (HNF4α)-responsive elements (HNF4RE1 and HNF4RE2) and one carbohydrate-responsive element-binding protein (ChREBP)-responsive element (ChoRE1). Deletion and mutation of HNF4RE1 and HNF4RE2 or ChoRE1 abolished HNF4α and ChREBP responsiveness, respectively. HNF4α and ChREBP synergistically stimulated Tkfc promoter activity. ChoRE1 mutation attenuated but maintained HNF4α responsiveness, whereas HNF4RE1 and HNF4RE2 mutations abolished ChREBP responsiveness. Moreover, Tkfc promoter activity stimulation by ChREBP was attenuated upon HNF4α knockdown. Furthermore, Tkfc expression was decreased in livers of ChREBP-/- and liver-specific HNF4-/- (Hnf4αΔHep) mice. Altogether, our data indicate that Tkfc is a target gene of ChREBP and HNF4α, and Tkfc promoter activity stimulation by ChREBP requires HNF4α.

Synthesis of Dicarboxylic Acids Comprising an Ether Linkage and Cyclic Skeleton and Its Further Application for High-Performance Aluminum Electrolyte Capacitors.

Aluminum electrolytic capacitors are essential components in all electronic devices, and it is known that their longevity depends on the performance of their electrolytes. We synthesized dicarboxylic acids having ether bonds showing the good solubility in ethylene glycol as a solvent and simultaneously developed a complete halogen removal method, which is strictly prohibited in capacitors. Moreover, the incorporation of bulky α-substituents and cyclic structures dramatically improved their heat resistance and can withstand high voltage, i.e., 764 V.

Establishment of a cell culture platform for human liver organoids and its application for lipid metabolism research.

Human liver organoids (HLOs) are reliable tools to represent physiological human liver biology. However, their use is limited especially in basic sciences. One of the reasons for this would be the insufficient systematic methodology to handle HLOs, including culture system, functional assessment, and gene transduction. Here, we generated and characterized mouse L cells stably and simultaneously overexpressing R-spondin1, hepatocyte growth factor, fibroblast growth factor (FGF) 7, and FGF10 via lentiviral transduction. The conditioned medium of the cells contributed to HLO growth as a replacement of commercially available recombinant proteins, which leads to a significant reduction of their culture cost. Proliferative and maturation phases of the cells were controlled by switching the medium to facilitate the evaluation of hepatocyte function, including insulin responsiveness and intracellular lipid accumulation. Gene expression analysis revealed that HLOs highly expressed genes involved in lipid metabolism. Importantly, HLOs secreted physiologically matured very low-density lipoprotein, which is rarely observed in mice and in established cell lines. Efficient gene transduction into HLOs was achieved via a transient 2-dimensional culture during viral infection. This study provides an invaluable platform for utilizing HLOs in various research fields, such as molecular biology, pharmacology, toxicology, and regenerative medicine.

Drug cytotoxicity screening using human intestinal organoids propagated with extensive cost-reduction strategies.

Organoids are regarded as physiologically relevant cell models and useful for compound screening for drug development; however, their applications are currently limited because of the high cost of their culture. We previously succeeded in reducing the cost of human intestinal organoid culture using conditioned medium (CM) of L cells co-expressing Wnt3a, R-spondin1, and Noggin. Here, we further reduced the cost by replacing recombinant hepatocyte growth factor with CM. Moreover, we showed that embedding organoids in collagen gel, a more inexpensive matrix than Matrigel, maintains organoid proliferation and marker gene expression similarly when using Matrigel. The combination of these replacements also enabled the organoid-oriented monolayer cell culture. Furthermore, screening thousands of compounds using organoids expanded with the refined method identified several compounds with more selective cytotoxicity against organoid-derived cells than Caco-2 cells. The mechanism of action of one of these compounds, YC-1, was further elucidated. We showed that YC-1 induces apoptosis through the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway, the mechanism of which was distinct from cell death caused by other hit compounds. Our cost-cutting methodology enables large-scale intestinal organoid culture and subsequent compound screening, which could expand the application of intestinal organoids in various research fields.

Intramolecular cyclization reactions of arylpropargyl amides of electron-deficient α,ß-alkenyl carboxylates and related compounds.

Intramolecular cyclization reactions of arylpropargyl amides of electron-deficient α,ß-alkenyl carboxylates such as fumarates and ethenetricarboxylates were investigated. The reaction of the fumaramides with a base, Et3N or DBU in xylenes at 140 °C under air gave benz[f]isoindoline derivatives in 21-63% yields. The benz[f]isoindolines may be produced via the formation of an allenic intermediate, intramolecular Diels-Alder reaction, proton transfer, and dehydrogenation by oxygen. The suitable bases and the product yields depend on the substituents on the benzene ring. On the other hand, the reaction of the amides of fumarate and ethenetricarboxylate by heating in DMSO gave aroyl-substituted pyrrolidine derivatives as major products, probably via addition of water under metal-free conditions. Furthermore, cyclization reactions of H and Me substituted alkyne derivatives were investigated for comparison. The selective formation of various types of products, such as ethyl 2-(1-benzyl-4-formyl-2-oxopyrrolidin-3-yl)acetate and diethyl 2-(1-benzyl-2-oxo-4-vinylidenepyrrolidin-3-yl)malonate, was found, depending upon the alkyne substituents and the reaction conditions. The reaction mechanisms have been discussed using density functional theory (DFT) calculations.

Hydroxylation site-specific and production-dependent effects of endogenous oxysterols on cholesterol homeostasis: Implications for SREBP-2 and LXR.

The cholesterol metabolites, oxysterols, play central roles in cholesterol feedback control. They modulate the activity of two master transcription factors that control cholesterol homeostatic responses, sterol regulatory element-binding protein-2 (SREBP-2) and liver X receptor (LXR). Although the role of exogenous oxysterols in regulating these transcription factors has been well established, whether endogenously synthesized oxysterols similarly control both SREBP-2 and LXR remains poorly explored. Here, we carefully validate the role of oxysterols enzymatically synthesized within cells in cholesterol homeostatic responses. We first show that SREBP-2 responds more sensitively to exogenous oxysterols than LXR in Chinese hamster ovary cells and rat primary hepatocytes. We then show that 25-hydroxycholesterol (25-HC), 27-hydroxycholesterol, and 24S-hydroxycholesterol endogenously synthesized by CH25H, CYP27A1, and CYP46A1, respectively, suppress SREBP-2 activity at different degrees by stabilizing Insig (insulin-induced gene) proteins, whereas 7α-hydroxycholesterol has little impact on SREBP-2. These results demonstrate the role of site-specific hydroxylation of endogenous oxysterols. In contrast, the expression of CH25H, CYP46A1, CYP27A1, or CYP7A1 fails to induce LXR target gene expression. We also show the 25-HC production-dependent suppression of SREBP-2 using a tetracycline-inducible CH25H expression system. To induce 25-HC production physiologically, murine macrophages are stimulated with a Toll-like receptor 4 ligand, and its effect on SREBP-2 and LXR is examined. The results also suggest that de novo synthesis of 25-HC preferentially regulates SREBP-2 activity. Finally, we quantitatively determine the specificity of the four cholesterol hydroxylases in living cells. Based on our current findings, we conclude that endogenous side-chain oxysterols primarily regulate the activity of SREBP-2, not LXR.

Long-term outcome and risk factors associated with events in patients with atrial fibrillation treated with oral anticoagulants: The ASSAF-K registry.

BACKGROUND: Oral anticoagulant therapy for atrial fibrillation (AF) has changed dramatically. Direct oral anticoagulant (DOAC) therapy is administered by general practitioners and specialists. However, the beneficial long-term effects and safety of DOACs have not been well investigated in real-world clinical practice. METHODS: The ASSAF-K (a study of the safety and efficacy of OAC therapy in the treatment of AF in Kanagawa), a prospective, multi-center, observational study, was conducted to clarify patient characteristics, status of OAC treatment, long-term outcomes, and adverse events, including cerebrovascular disease, bleeding, and death. RESULTS: A total of 4014 patients were enrolled (hospital: 2500 cases; clinic: 1514 cases). The number of patients in the final dataset was 3367 (mean age, 72.6 ±â€¯10.0 years; males, 66.3 %). CHA2DS2-VASc and HAS-BLED scores were 3.0 ±â€¯1.6 and 2.2 ±â€¯1.0, respectively. The risk factors of the primary composite outcome (all-cause death, serious bleeding events, cerebral hemorrhage, and stroke) were higher age, lower body mass index, lower diastolic blood pressure, lower creatine clearance, history of heart failure, history of stroke, and medication of anti-platelet agents. The event-free rates of the primary composite outcome with DOACs, warfarin, and without OACs were 92.7 %, 88.0 %, and 87.4 %, respectively. The event rate of DOACs was significantly lower than that of warfarin [HR 0.63 (95 % CI 0.48-0.81)], and similar results were observed after adjustment for AF stroke risk score [HR 0.70 (95 % CI 0.54-0.90)]. Serious bleeding events tended to occur less frequently with DOACs compared with warfarin [unadjusted HR 0.53 (95 % CI 0.31-0.91), adjusted HR 0.61 (95 % CI 0.33-1.11)]. CONCLUSIONS: This multi-center registry demonstrated the long-term outcome in patients with AF treated with and without OACs and suggests that DOAC therapy is safe and beneficial in hospitals and clinics.

Pathophysiological levels of GDF11 activate Smad2/Smad3 signaling and induce muscle atrophy in human iPSC-derived myocytes.

Skeletal muscle mass is negatively regulated by several TGF-ß superfamily members. Myostatin (MSTN) is the most prominent negative regulator of muscle mass. Recent studies show that in addition to MSTN, GDF11, which shares a high sequence identity with MSTN, induces muscle atrophy in vitro and in vivo at supraphysiological levels, whereas controversy regarding its roles exists. Furthermore, higher circulating GDF11 levels associate with frailty in humans. On the other hand, little is known about the effect of pathophysiological levels of GDF11 on muscle atrophy. Here we seek to determine whether pathophysiological levels of GDF11 are sufficient to activate Smad2/Smad3 signaling and induce muscle atrophy using human iPSC-derived myocytes (hiPSC myocytes). We first show that incubating hiPSC myocytes with pathophysiological concentrations of GDF11 significantly reduces myocyte diameters. We next demonstrate that pathophysiological levels of GDF11 are sufficient to activate Smad2/3 signaling. Finally, we show that pathophysiological levels of GDF11 are capable of inducing the expression of Atrogin-1, an atrophy-promoting E3 ubiquitin ligase and that FOXO1 blockage reverses the GDF11-induced Atrogin-1 expression and atrophic phenotype. Collectively, our results suggest that GDF11 induces skeletal muscle atrophy at the pathophysiological levels through the GDF11-FOXO1 axis.

Lactic acid bacteria-derived γ-linolenic acid metabolites are PPARδ ligands that reduce lipid accumulation in human intestinal organoids.

Gut microbiota regulate physiological functions in various hosts, such as energy metabolism and immunity. Lactic acid bacteria, including Lactobacillus plantarum, have a specific polyunsaturated fatty acid saturation metabolism that generates multiple fatty acid species, such as hydroxy fatty acids, oxo fatty acids, conjugated fatty acids, and trans-fatty acids. How these bacterial metabolites impact host physiology is not fully understood. Here, we investigated the ligand activity of lactic acid bacteria-produced fatty acids in relation to nuclear hormone receptors expressed in the small intestine. Our reporter assays revealed two bacterial metabolites of γ-linolenic acid (GLA), 13-hydroxy-cis-6,cis-9-octadecadienoic acid (γHYD), and 13-oxo-cis-6,cis-9-octadecadienoic acid (γKetoD) activated peroxisome proliferator-activated receptor delta (PPARδ) more potently than GLA. We demonstrate that both γHYD and γKetoD bound directly to the ligand-binding domain of human PPARδ. A docking simulation indicated that four polar residues (T289, H323, H449, and Y473) of PPARδ donate hydrogen bonds to these fatty acids. Interestingly, T289 does not donate a hydrogen bond to GLA, suggesting that bacterial modification of GLA introducing hydroxy and oxo group determines ligand selectivity. In human intestinal organoids, we determined γHYD and γKetoD increased the expression of PPARδ target genes, enhanced fatty acid ß-oxidation, and reduced intracellular triglyceride accumulation. These findings suggest that γHYD and γKetoD, which gut lactic acid bacteria could generate, are naturally occurring PPARδ ligands in the intestinal tract and may improve lipid metabolism in the human intestine.

Development of a novel peptide inhibitor of subtilisin BPN'.

Proteinaceous protease inhibitors can strongly and specifically inhibit cognate proteases, but their use as pharmaceuticals is limited by their size. As such, the development of effective protease peptide inhibitors would be beneficial for biochemical studies and drug discovery. In this study, we applied a phage display system to select subtilisin BPN'-binding peptides and evaluated their inhibitory activities against subtilisin BPN'. A 12mer peptide with an intramolecular disulfide bond inhibited subtilisin BPN' (Ki value of 13.0 nm). Further mutational analyses of the peptide resulted in the development of a short peptide inhibitor against subtilisin BPN' that showed high inhibitory activity and binding affinity (Ki value of 0.30 nm). This activity was found to be derived from the conformational rigidity caused by the intramolecular disulfide bond and the small residue at the P1' site and from the interaction of the P4 and P6' residues with subtilisin BPN'.

Signaling Pathway of Taurine-Induced Upregulation of TXNIP.

Taurine, a sulfur-containing ß-amino acid, is present at high concentrations in mammalian tissues and plays an important role in several essential biological processes. However, the genetic mechanisms involved in these physiological processes associated with taurine remain unclear. In this study, we investigated the regulatory mechanism underlying the taurine-induced transcriptional enhancement of the thioredoxin-interacting protein (TXNIP). The results showed that taurine significantly increased the luciferase activity of the human TXNIP promoter. Further, deletion analysis of the TXNIP promoter showed that taurine induced luciferase activity only in the TXNIP promoter region (+200 to +218). Furthermore, by employing a bioinformatic analysis using the TRANSFAC database, we focused on Tst-1 and Ets-1 as candidates involved in taurine-induced transcription and found that the mutation in the Ets-1 sequence did not enhance transcriptional activity by taurine. Additionally, chromatin immunoprecipitation assays indicated that the binding of Ets-1 to the TXNIP promoter region was enhanced by taurine. Taurine also increased the levels of phosphorylated Ets-1, indicating activation of Ets-1 pathway by taurine. Moreover, an ERK cascade inhibitor significantly suppressed the taurine-induced increase in TXNIP mRNA levels and transcriptional enhancement of TXNIP. These results suggest that taurine enhances TXNIP expression by activating transcription factor Ets-1 via the ERK cascade.

Nobiletin enhances plasma Interleukin-6 and C-X-C motif chemokine ligand 1 levels that are increased by treadmill running.

Exercise increases the muscular secretion of Interleukin-6 (IL-6), which is partially regulated by ß2-adrenergic receptor signaling. Nobiletin is a polymethoxyflavone (PMF) found in citrus fruits that induces the secretion of IL-6 from C2C12 myotubes, but it remains unclear whether nobiletin promotes IL-6 secretion during exercise. The aim of this study was to clarify the effects of nobiletin on IL-6 secretion during exercise. Nobiletin and epinephrine were found to synergistically increase IL-6 secretion from differentiated C2C12 cells, which was suppressed by the inhibition of adenylyl cyclase (AC) or protein kinase A (PKA). Treadmill running for 60 min increased plasma levels of IL-6, epinephrine, and norepinephrine in rats. Nobiletin (5 mg/kg) orally administered 30 min before running increased plasma IL-6 levels further, although it did not increase plasma epinephrine and norepinephrine. In a similar manner to IL-6, nobiletin and epinephrine synergistically increased the secretion of C-X-C motif chemokine ligand 1 (CXCL-1) from C2C12 cells, or the increase in plasma CXCL-1 was enhanced by nobiletin after treadmill running of rats. Our results suggest that nobiletin promotes IL-6 and CXCL-1 secretion from skeletal muscle by synergistic enhancement of the PKA pathway in ß2-adrenergic receptor signaling.

Organoid-derived intestinal epithelial cells are a suitable model for preclinical toxicology and pharmacokinetic studies.

Intestinal organoids are physiologically relevant tools used for cellular models. However, the suitability of organoids to examine biological functions over existing established cell lines lacks sufficient evidence. Cytochrome P450 3A4 (CYP3A4) induction by pregnane X receptor ligands, glucose uptake via sodium/glucose cotransporter 1, and microsomal triglyceride transfer protein-dependent ApoB-48 secretion, which are critical for human intestinal metabolism, were observed in organoid-derived two-dimensional cells but little in Caco-2 cells. CYP3A4 induction evaluation involved a simplified method of establishing organoids that constitutively expressed a reporter gene. Compound screening identified several anticancer drugs with selective activities toward Caco-2 cells, highlighting their characteristics as cancer cells. Another compound screening revealed a decline in N-(4-hydroxyphenyl)retinamide cytotoxicity upon rifampicin treatment in organoid-derived cells, under CYP3A4-induced conditions. This study shows that organoid-derived intestinal epithelial cells (IECs) possess similar physiological properties as intestinal epithelium and can serve as tools for enhancing the prediction of biological activity in humans.

Emission bandwidth control on a two-dimensional superlattice microcavity array.

Narrowband thermal emission at high temperatures is required for various thermal energy systems. However, the large lossy energy of refractory metals induces a broad bandwidth emission. Here, we demonstrated a two-dimensional (2D) superlattice microcavity array on refractory metals to control the emission bandwidth. A hybrid resonance mode was obtained by coupling the standing-wave modes and propagating surface-wave modes. The bandwidth emission was controlled by varying the superlattice microcavity array resulting from the change in electric field (E-field) concentration. The quality factor (Q-factor) improved by more than 3 times compared to that of a single-lattice array. A narrower band emission originating from the hybrid mode was observed and analyzed experimentally. This novel surface-relief microstructure method can be used to control the emission bandwidth of thermal emitters used in thermophotovoltaic (TPV) systems and other high-temperature thermal energy systems.

Sesamin and Hepatic Metabolites Derived from Sesamin and Episesamin Antagonize Farnesoid X Receptor and Reduce the Expression of Gluconeogenesis-Related Genes.

Sesamin and episesamin are the main lignans found in refined sesame oil and have been reported to exert various health benefits. However, the health benefits of these lignans and their molecular mechanisms have not been fully understood. This study evaluated the effects of sesamin, episesamin, and their metabolites on the nuclear bile acid receptor, farnesoid X receptor (FXR, NR1H4), which regulate gene expression involved in bile acid metabolism and gluconeogenesis. By using two different cell-based luciferase reporter assay systems, we found that sesamin, sesamin metabolites, and some episesamin metabolites inhibited FXR activation driven by a bile acid and a synthesized agonist, and it is suggested that these compounds exert their antagonist activity by competing with the FXR agonists on the ligand-binding domain. Sesamin and its major metabolite SC-1 suppressed the expression of several gluconeogenesis-related genes governed by FXR in HepG2 cells but did not affect the expression level of CYP7A1, the rate-limiting enzyme for bile acid synthesis. Dietary sesamin supplementation (AIN-93G supplemented with 0.5% sesamin) led to the decreased hepatic expression of several gluconeogenesis-related genes and reduced blood glucose levels in mice, without adverse effects on bile acid metabolism. These results shed light on the health benefits of taking sesamin and episesamin.

Multiband infrared emissions limited in the grazing angle from metal-dielectric-metal metamaterials.

Thermal radiation management remains a challenge because of the incoherent and isotropic nature of electromagnetic waves. In this study, a multiband and angular-selective infrared emitter, consisting of a simple one-dimensional (1D) metal-dielectric-metal metamaterial, is demonstrated. Although this structure has been well known as spectrally selective emitters, we analytically reveal that when the dielectric layer thickness is much smaller than the wavelength of interest (< 1/10), directive emission at nearly equal to the grazing angles (> 80°) can be obtained at multiple resonant wavelengths. As the absorption peaks can be entirely characterized by geometrical parameters, this angular selective technology offers flexible control of thermal radiation and can be adjusted to specific applications.

Endocrine Fibroblast Growth Factors in Relation to Stress Signaling.

Fibroblast growth factors (FGFs) play important roles in various growth signaling processes, including proliferation, development, and differentiation. Endocrine FGFs, i.e., atypical FGFs, including FGF15/19, FGF21, and FGF23, function as endocrine hormones that regulate energy metabolism. Nutritional status is known to regulate the expression of endocrine FGFs through nuclear hormone receptors. The increased expression of endocrine FGFs regulates energy metabolism processes, such as fatty acid metabolism and glucose metabolism. Recently, a relationship was found between the FGF19 subfamily and stress signaling during stresses such as endoplasmic reticulum stress and oxidative stress. This review focuses on endocrine FGFs and the recent progress in FGF studies in relation to stress signaling. In addition, the relevance of the stress-FGF pathway to disease and human health is discussed.

Skeletal muscle releases extracellular vesicles with distinct protein and microRNA signatures that function in the muscle microenvironment.

Extracellular vesicles (EVs) contain various regulatory molecules and mediate intercellular communications. Although EVs are secreted from various cell types, including skeletal muscle cells, and are present in the blood, their identity is poorly characterized in vivo, limiting the identification of their origin in the blood. Since skeletal muscle is the largest organ in the body, it could substantially contribute to circulating EVs as their source. However, due to the lack of defined markers that distinguish skeletal muscle-derived EVs (SkM-EVs) from others, whether skeletal muscle releases EVs in vivo and how much SkM-EVs account for plasma EVs remain poorly understood. In this work, we perform quantitative proteomic analyses on EVs released from C2C12 cells and human iPS cell-derived myocytes and identify potential marker proteins that mark SkM-EVs. These markers we identified apply to in vivo tracking of SkM-EVs. The results show that skeletal muscle makes only a subtle contribution to plasma EVs as their source in both control and exercise conditions in mice. On the other hand, we demonstrate that SkM-EVs are concentrated in the skeletal muscle interstitium. Furthermore, we show that interstitium EVs are highly enriched with the muscle-specific miRNAs and repress the expression of the paired box transcription factor Pax7, a master regulator for myogenesis. Taken together, our findings confirm previous studies showing that skeletal muscle cells release exosome-like EVs with specific protein and miRNA profiles in vivo and suggest that SkM-EVs mainly play a role within the muscle microenvironment where they accumulate.

Valerenic Acid Promotes Adipocyte Differentiation, Adiponectin Production, and Glucose Uptake via Its PPARγ Ligand Activity.

Although valerenic acid (VA) is an important marker compound for quantitative assessment of Valeriana officinalis products, little is known about its potential effects on adipocytes. We investigated the effects of VA on adipocyte differentiation, adiponectin production, and glucose uptake using 3T3-L1 adipocytes. The results showed that VA promoted adipocyte differentiation and increased the gene expression of adipogenesis and glucose uptake-related proteins, including peroxisome proliferator-activated receptor gamma (PPARγ), cytosine-cytosine-adenosine-adenosine-thymidine enhancer binding protein alpha (C/EBPα), adiponectin, and glucose transporter 4 (GLUT4). Additionally, cell cultures treated with VA had elevated adiponectin secretion and glucose uptake. The PPARγ luciferase assay indicated VA as a partial agonist of PPARγ, while the analysis using its antagonist, GW9662, and a docking simulation between PPARγ and VA revealed the binding site of VA as likely adjacent to the Ω loop pocket of PPARγ. Taken together, these results demonstrate that VA acts as a PPARγ partial agonist to promote adipocyte differentiation, adiponectin production, and glucose uptake.

Inhibitory Effect of Tangeretin and Cardamonin on Human Intestinal SGLT1 Activity In Vitro and Blood Glucose Levels in Mice In Vivo.

Rapid postprandial blood glucose elevation can cause lifestyle-related diseases, such as type II diabetes. The absorption of food-derived glucose is primarily mediated by sodium/glucose cotransporter 1 (SGLT1). Moderate SGLT1 inhibition can help attenuate postprandial blood glucose elevation and prevent lifestyle-related diseases. In this study, we established a CHO cell line stably expressing human SGLT1 and examined the effects of phytochemicals on SGLT1 activity. Among the 50 phytochemicals assessed, tangeretin and cardamonin inhibited SGLT1 activity. Tangeretin and cardamonin did not affect the uptake of L-leucine, L-glutamate, and glycyl-sarcosine. Tangeretin, but not cardamonin, inhibited fructose uptake, suggesting that the inhibitory effect of tangeretin was specific to the monosaccharide transporter, whereas that of cardamonin was specific to SGLT1. Kinetic analysis suggested that the suppression of SGLT1 activity by tangeretin was associated with a reduction in Vmax and an increase in Km, whereas suppression by cardamonin was associated with a reduction in Vmax and no change in Km. Oral glucose tolerance tests in mice showed that tangeretin and cardamonin significantly suppressed the rapid increase in blood glucose levels. In conclusion, tangeretin and cardamonin were shown to inhibit SGLT1 activity in vitro and lower blood glucose level in vivo.