von Willebrand factor Ristocetin co-factor activity to von Willebrand factor antigen level ratio for diagnosis of acquired von Willebrand syndrome caused by aortic stenosis.

Background: Severe aortic stenosis (AS) causes acquired von Willebrand syndrome by the excessive shear stress-dependent cleavage of high molecular weight multimers of von Willebrand factor (VWF). While the current standard diagnostic method is so-called VWF multimer analysis that is western blotting under nonreducing conditions, it remains unclear whether a ratio of VWF Ristocetin co-factor activity (VWF:RCo) to VWF antigen levels (VWF:Ag) of <0.7, which can be measured with an automated coagulation analyzer in clinical laboratories and is used for the diagnosis of hereditary von Willebrand disease. Objectives: To evaluated whether the VWF:RCo/VWF:Ag is useful for the diagnosis of AS-induced acquired von Willebrand syndrome. Methods: VWF:RCo and VWF:Ag were evaluated with the VWF large multimer index as a reference, which represents the percentage of a patient's VWF high molecular weight multimer ratio to that of standard plasma in the VWF multimer analysis. Results: We analyzed 382 patients with AS having transaortic valve maximal pressure gradients of >30 mmHg, 27 patients with peripheral artery disease, and 46 control patients free of cardiovascular disease with osteoarthritis, diabetes, and so on. We assumed a large multimer index of <80% as loss of VWF large multimers since 59.0% of patients with severe AS had the indices of <80%, while no control patients or patients with peripheral artery disease, except for 2 patients, exhibited the indices of <80%. The VWF:RCo/VWF:Ag ratios, measured using an automated blood coagulation analyzer, were correlated with the indices (rs = 0.470, P < .001). When the ratio of <0.7 was used as a cut-off point, the sensitivity and specificity to VWF large multimer indices of <80% were 0.437 and 0.826, respectively. Conclusion: VWF:RCo/VWF:Ag ratios of <0.7 may indicate loss of VWF large multimers with high specificity, but low sensitivity. VWF:RCo/VWF:Ag ratios in patients with AS having a ratio of <0.7 may be useful for monitoring the loss of VWF large multimers during their clinical courses.

Increased cleavage of von Willebrand factor by ADAMTS13 may contribute strongly to acquired von Willebrand syndrome development in patients with essential thrombocythemia.

BACKGROUND: Patients with essential thrombocythemia (ET) often experience bleeding associated with acquired von Willebrand syndrome (AVWS) when the platelet count is markedly increased. OBJECTIVE: We investigated whether von Willebrand factor (VWF) degradation is enhanced in patients with ET. METHODS: Seventy patients with ET underwent VWF multimer (VWFM) analysis and measurement of VWF-related parameters. We calculated the VWFM index, defined as the ratio of intensities of a patient's molecular weight-categorized VWFMs, and those of a healthy subject's, using densitometric analysis. VWF degradation product (DP) was measured via ELISA using a monoclonal antibody that specifically recognizes Y1605 at the C-terminal boundary, which is exposed following ADAMTS13-mediated cleavage of the Y1605-M1606 bond of the VWF A2 domain. RESULTS: Patients with higher platelet counts had a significantly reduced high molecular weight (HMW)-VWFM index and an increased VWF-DP:VWF antigen (Ag) ratio compared to those with lower platelet counts. On multivariate analysis, the VWF-DP/VWF:Ag ratio was an independent predictor of the HMW-VWFM index. Patients who underwent cytoreductive therapy had a significantly higher HMW-VWFM index and lower VWF-DP/VWF:Ag ratio than those who did not. Among individual patients, there was also a significant increase in the HMW-VWFM index and a decrease in the VWF-DP/VWF:Ag ratio after cytoreductive therapy compared to pre-therapy values. CONCLUSION: In patients with ET, an increased platelet count is associated with enhanced cleavage of VWF at the Y1605-M1606 bond, primarily by ADAMTS13, leading to AVWS. Cytoreductive therapy reduces the platelet count, prevents excessive VWF cleavage, and improves VWFM distributions.

[Refractory thrombotic thrombocytopenic purpura complicated with multiple cerebral infarction].

Neuropsychiatric symptoms comprise one of the five classic symptoms of autoimmune thrombotic thrombocytopenic purpura (aTTP). Although aTTP is typically transient, it is sometimes complicated by cerebral infarction with residual disability. This report presents the case of an 87-year-old man previously admitted to a different hospital with fever and transient consciousness loss. After receiving platelet transfusion with diagnosis of Evans syndrome, he was transferred to our hospital with worsening consciousness disturbance. He was subsequently diagnosed with aTTP with a PLASMIC score of 6 points, ADAMTS13 activity of less than 0.5%, and its inhibitor of 7.4 BU/ml. Platelet count and consciousness were rapidly improved with plasmapheresis and steroids, but motor aphasia emerged. MRI showed multiple cerebral infarctions, including a large infarction in the left frontal lobe. Thus, unfractionated heparin was administered. When his platelet count dropped once again on the 20th day, rituximab was added. The treatment eventually proved to be successful, and his aTTP remained in remission one year after the onset. Treatment for cerebral infarctions was switched to DOAC, and rehabilitation was continued. However, his ADL has not yet recovered. Advances in aTTP treatment have cured many similar cases. Thus, rituximab is now considered a treatment option for refractory cases. However, ischemic organ damage in acute phase and sequelae are observed. Therefore, early diagnosis and novel therapy are required.

Optimization of anti-ADAMTS13 antibodies for the treatment of ADAMTS13-related bleeding disorder in patients receiving circulatory assist device support.

ADAMTS13 (a disintegrin-like and metalloproteinase with thrombospondin type-1 motif 13)-related bleeding disorder has been frequently observed as a life-threatening clinical complication in patients carrying a circulatory assist device. Currently, treatment modalities for the bleeding disorder are very limited and not always successful. To address the unmet medical need, we constructed humanized antibodies of mouse anti-ADAMTS13 antibody A10 (mA10) by using complementarity-determining region (CDR) grafting techniques with human antibody frameworks, 8A7 and 16E8. The characteristics of the two humanized A10 antibodies, namely A10/8A7 and A10/16E8, were assessed in vitro and in silico. Among the two humanized A10 antibodies, the binding affinity of A10/16E8 to ADAMTS13 was comparable to that of mA10 and human-mouse chimeric A10. In addition, A10/16E8 largely inhibited the ADAMTS13 activity in vitro. The results indicated that A10/16E8 retained the binding affinity and inhibitory activity of mA10. To compare the antibody structures, we performed antibody structure modeling and structural similarity analysis in silico. As a result, A10/16E8 showed higher structural similarity to mA10, compared with A10/8A7, suggesting that A10/16E8 retains a native structure of mA10 as well as its antigen binding affinity and activity. A10/16E8 has great potential as a therapeutic agent for ADAMTS13-related bleeding disorder.

Analysis focusing on plasma von Willebrand factor in pachychoroid neovasculopathy and age-related macular degeneration.

Pachychoroid neovasculopathy (PNV) is a new concept of macular disorder. Some cases diagnosed as age-related macular degeneration (AMD) have been re-diagnosed as PNV. However, the biological features of PNV are still uncertain. The purpose of this study was to compare PNV and AMD by analyses focusing on von Willebrand factor (VWF) and complement factor H (CFH). Ninety-seven patients who were previously diagnosed with treatment naïve AMD were enrolled in this study. They were re-classified as either PNV or AMD based on the clinical criteria and 33 patients were classified as PNV and 64 patients as AMD. We examined the clinical data, analyzed VWF multimer and two genetic polymorphisms (I62V and Y402H) in the CFH. PNV group was significantly younger than AMD group (P = 0.001). In both I62V and Y402H, there were no significant differences between PNV and AMD while the recessive homozygous (AA) was found only in PNV group in I62V. The presence of unusually large VWF multimers (UL-VWFMs) and subretinal hemorrhages were significantly higher in PNV than in AMD (P = 0.045, P = 0.020, respectively). Thus, the residual UL-VWFMs may result in platelet thrombosis and hemorrhages in the choriocapillaris of PNV. In conclusion, our results suggest the biological differences between PNV and AMD.

Strong association between insufficient plasma exchange and fatal outcomes in Japanese patients with immune-mediated thrombotic thrombocytopenic purpura.

Plasma exchange (PEX) using fresh frozen plasma has considerably reduced the mortality rate in patients with immune-mediated thrombotic thrombocytopenic purpura (iTTP). However, some patients still do not survive even with treatment, but little information is available regarding which treatment these patients received. This study was conducted to obtain this information in 240 patients who met the current iTTP diagnostic criteria and completed at least 30 days of follow-up except for deceased cases. These patients were divided into three groups: survivors (n = 195), TTP-related deaths (n = 32), and other cause of death (n = 13). In the TTP-related death group, 26 of 32 patients experienced sudden death, mostly following radical hypotension and bradycardia. The median follow-up time after admission was 5.0 days, and the median number of PEX sessions was 2.5. Nine patients underwent autopsy and had cardiac microvascular thrombi in arterioles. Levels of lactate dehydrogenase, total bilirubin, serum creatinine, and D-dimer were significantly higher in the TTP-related death group than in the survivors group. Frequent PEX (> 20 sessions) was not associated with TTP-related death. In the acute phase of iTTP, patients with substantial organ damage caused by microthrombi have a greater mortality risk, even after just a few PEX sessions.

Hemolysis and von Willebrand factor degradation in mechanical shuttle shear flow tester.

Chronic blood trauma caused by the shear stresses generated by mechanical circulatory support (MCS) systems is one of the major concerns to be considered during the development of ventricular assist devices. Large multimers with high-molecular-weight von Willebrand factor (VWF) are extended by the fluid forces in a shear flow and are cleaved by ADAMTS13. Since the mechanical revolving motions in artificial MCSs induce cleavage in large VWF multimers, nonsurgical bleeding associated with the MCS is likely to occur after mechanical hemodynamic support. In this study, the shear stress (~ 600 Pa) and exposure time related to hemolysis and VWF degradation were investigated using a newly designed mechanical shuttle shear flow tester. The device consisted of a pair of cylinders facing the test section of a small-sized pipe; both the cylinders were connected to composite mechanical heads with a sliding-sleeve structure for axial separation during the withdrawing motion. The influence of exposure time, in terms of the number of stress cycles, on hemolysis and VWF degradation was confirmed using fresh goat blood, and the differences in the rates of dissipation of the multimers were established. The plasma-free hemoglobin levels showed a logarithmic increase corresponding to the number of cycles, and the dissipation of large VWF multimers occurred within a few seconds under high shear stress flow conditions.

Characteristics Behaviors of Coagulation and Fibrinolysis Markers in Acquired Thrombotic Thrombocytopenic Purpura.

INTRODUCTIONS: Patients with acquired thrombotic thrombocytopenic purpura (TTP) show no severe abnormalities in coagulation or fibrinolysis. However, the exact extent of the abnormalities is unclear. MATERIALS AND METHODS: This study analyzed 138 patients with acquired TTP and 46 patients with septic disseminated intravascular coagulation (DIC) who were included in a Japanese registry. Complete blood cell counts and 8 coagulation or fibrinolysis parameters were compared between the 2 groups. RESULTS: Platelet counts in the acquired TTP group were significantly lower than those in the septic DIC group (P < .001). The international normalized ratio of prothrombin time and the activated partial thromboplastin time in the septic DIC group were significantly higher and longer, respectively, than those in the acquired TTP group (P < .01). The antithrombin (AT) values were significantly lower in the septic DIC group than in the acquired TTP group (P < .001), the latter of which were almost normal. Although both groups revealed elevations of fibrinogen degradation product (FDP) and D-dimer, these levels were significantly higher in the septic DIC group than in the acquired TTP group (P < .001). Of 138 patients with acquired TTP, 25 (18.1%) were diagnosed with septic DIC by the diagnostic criteria of the Japanese Ministry Health, Labour and Welfare, and 78 (56.5%) by those of the Japanese Association of Acute Medicine. Receiver operating characteristic curve analysis showed that acquired TTP could be diagnosed based on severe thrombocytopenia (<20 × 109/L), normal AT level (>87%), and mildly elevated FDP (<23 µg/mL). CONCLUSIONS: Our results indicate that 3 routine laboratory tests could differentiate between acquired TTP and septic DIC.

Management of a COVID-19 Patient during ECMO: Paying Attention to Acquired von Willebrand Syndrome.

Patients with severe COVID-19 often experience complications including coagulopathy and fatal thrombosis. COVID-19 pneumonia sometimes leads to acute respiratory distress syndrome, requiring extracorporeal membrane oxygenation (ECMO), during which thrombosis and bleeding are major causes of death. Anticoagulation such as heparin is essential for COVID-19 patients on ECMO; however, bleeding might be caused by not only heparin, but also acquired von Willebrand syndrome (AVWS). To date, no study has examined ECMO-related bleeding and AVWS in COVID-19 patients.We report a COVID-19 patient who experienced bleeding from AVWS in addition to disseminated intravascular coagulation (DIC) during ECMO. The level of high-molecular weight VWF multimers decreased during ECMO therapy, and these findings promptly improved after discontinuation of ECMO. Plasma levels of VWF antigen were extremely high, probably due to endothelial cell damage caused by COVID-19. On the other hand, plasma levels of ADAMTS13 activity were moderately reduced, to 20-30% of normal. The patient was successfully treated with cryoprecipitate in bleeding during ECMO without a reduction in heparin, which might have induced thromboembolism. Bleeding found in this patient might be caused by AVWS and DIC.Severe COVID-19 patients are in a thrombotic state and need to receive anticoagulant therapy. However, once they receive ECMO therapy, bleeding symptoms could be observed. In such cases, physicians should think of AVWS in addition to the side effect of heparin and DIC.

Rituximab prolongs the time to relapse in patients with immune thrombotic thrombocytopenic purpura: analysis of off-label use in Japan.

Immune thrombotic thrombocytopenic purpura (iTTP) is caused by ADAMTS13 deficiency due to anti-ADAMTS13 autoantibodies. Rituximab, an anti-CD20 monoclonal antibody, is often used to suppress these autoantibodies. This retrospective study, conducted in an iTTP cohort in Japan, evaluated the long-term efficacy of rituximab as off-label treatment for refractory or relapsed cases. A total of 252 iTTP patients with severe ADAMTS13 deficiency (< 10%) and its inhibitor were enrolled, and 169 episodes in 156 patients were analyzed. Sixty-five episodes with relapse or resistance to conventional treatment were treated with rituximab, while 104 episodes received conventional treatment only. The rituximab group had a significantly higher inhibitor titer than the rituximab-untreated group. During the median follow-up period of 3.9 years, there were 8 relapses in the rituximab group and 17 relapses in the rituximab-untreated group. The median time to relapse in the rituximab group (2.9 years) was significantly longer than that in the rituximab-untreated group (1.2 years). Relapse-free survival at 2 years was significantly higher in the rituximab group than in the rituximab-untreated group. The incidence of relapse at 5 years did not differ between the 2 groups. Rituximab reduced the risk of relapse in refractory or relapsed iTTP patients for 2 years.

[Acquired von Willebrand syndrome].

Von Willebrand disease (VWD) is among the most common inherited bleeding disorders. Interestingly, acquired von Willebrand syndrome (AVWS) is diagnosed much less frequently, but can be identified in association with a substantial number of medical conditions and diseases, including lymphoproliferative (48%), cardiovascular (21%), myeloproliferative (15%), other neoplastic (5%), and autoimmune disorders (2%). Most recently, AVWS has been diagnosed in patients with aortic valve stenosis (AS, 79%) and continuous-flow left ventricular assist devices (LVAD, up to 100%).1) Immune mechanisms mediated reduction of VWF activityAutoantibodies to VWF have been identified in association with monoclonal gammopathies, lymphoid, neoplasms, and autoimmune diseases. Some autoantibodies have higher affinity to high molecular weight-VWF multimers (HMW-VWFMs); clearance of HMW-VWFMs leads to bleeding.2) Non-immune mechanisms induced reduction of VWF activityOne of the mechanisms is VWF adsorption onto malignant cells and paraproteins (i.e., as in multiple myeloma) and thereby removed from the blood circulation. VWF-linked proteolysis can be induced by shear stress. According to high levels of shear stress in AS and LVAD, HM-VWFMs are more susceptible to cleavage by ADAMTS13. We will find a large number of AVWS cases related to cardiovascular diseases.

[Successful management of acquired factor V deficiency developing shortly after induction of hemodialysis].

Autoimmune factor V deficiency (AiF5D) is caused by autoantibodies to coagulation factor V (FV); its clinical manifestations range from asymptomatic to fatal hemorrhage. Herein, we report the case of a 68-year-old man who was diagnosed with end-stage renal disease at the time of a femoral fracture and developed AiF5D after initiating hemodialysis. A wound infection that occurred after joint replacement was treated with antibiotics; however, it was poorly controlled. One month after the procedure, his coagulation time prolonged. The infection was improved by debridement and antibiotics; however, the coagulation time was not decreased and poor hemostasis at the shunt was still persistent. Because ELISA detected anti-FV-binding IgG with FV activity of <2.8% and FV inhibitor levels were 11.8 BU/ml, AiF5D was diagnosed. Oral prednisolone (PSL) was started. Dialysis was initially performed without anticoagulants, but blood clots were not found in the circuit. Anticoagulants were resumed when the coagulation time decreased. After achieving complete remission, PSL dose was tapered and finally discontinued. Few reports have described the management of AiF5D via dialysis. We consider that our report would be useful for the management of patients with similar manifestations.

Ischaemia-reperfusion injury with Pringle's maneuver induces unusually large von Willebrand factor multimers after hepatectomy.

INTRODUCTION: von Willebrand factor (VWF) is synthesised in vascular endothelial cells and released into the plasma as unusually large VWF multimers (UL-VWFMs). Sinusoidal endothelial cells are a major target of ischaemia-reperfusion injury due to liver surgery. This study aimed to clarify the effect of hepatectomy on UL-VWFMs. MATERIALS AND METHODS: Thirty-five patients who underwent hepatectomy were eligible for the study. Plasma ADAMTS13 activity and VWF antigen levels were measured by enzyme-linked immunosorbent assay and multimer analysis of plasma VWF was performed according to Ruggeri and Zimmerman's method. For analyses, patients were categorised according to UL-VWFM positivity after hepatectomy. RESULTS: Plasma ADAMTS13 activity significantly decreased from 61.0% (27.7%-126.2%) before operation to 37.4% (20.2%-71.4%) on postoperative day 7 (p < 0.001). Plasma VWF antigen levels significantly increased from 172.1% (80.5%-412.8%) before operation to 361.0% (154.7%-745.8%) on postoperative day 2, which remained high until postoperative day 7 (p < 0.001). Seven patients remained UL-VWFMs-negative and 22 patients became UL-VWFMs-positive after operation. Pringle's maneuver duration was significantly longer and blood loss volume was significantly higher in the UL-VWFMs-positive group (p = 0.001 and p = 0.003, respectively). By multivariable analysis, Pringle's maneuver duration [odds ratio 1.049, 95% confidence interval (CI) 1.001-1.098; p = 0.043] was significantly associated with increased UL-VWFMs level after hepatectomy. UL-VWFMs index was significantly correlated with Pringle's maneuver duration (r = 0.444, p = 0.017). CONCLUSIONS: Plasma UL-VWFMs levels increased after hepatectomy due to ischaemia-reperfusion injury with Pringle's maneuver.

Involvement of the ADAMTS13-VWF axis in acute Kawasaki disease and effects of intravenous immunoglobulin.

INTRODUCTION: ADAMTS13 modulates shear-dependent platelet thrombus formation (PTF) by limited proteolysis of von Willebrand factor (VWF). A high-plasma-ratio of VWF antigen to ADAMTS13 activity (VWF:Ag/ADAMTS13:AC) promotes PTF and aggravates shear-induced inflammation mediated by VWF. A role of ADAMTS13 in Kawasaki disease (KD) remains unknown, however. We investigated the involvement of ADAMTS13-VWF axis in the acute-phase of KD (acute-KD). METHODS: VWF:Ag and ADAMTS13:AC in 77 KD infants were measured at three time-points; immediately before (Pre), one-week (1 W) and one-month (1 M) after intravenous-immunoglobulin (IVIG) treatment. VWF multimer (VWFM) distribution and ADAMTS13-isoelectrofocusing (IEF) patterns were compared between the responders and non-responders to IVIG. RESULTS: A high VWF:Ag (195.7 ±â€¯85.6%, p < 0.05), low ADAMTS13:AC (60.3 ±â€¯23.8%, p < 0.05) and high VWF:Ag/ADAMTS13:AC ratio (3.70 ±â€¯2.12, p < 0.05) at Pre were seen compared to control plasmas. These parameters returned to normal levels time-dependently after IVIG treatment. Non-responders to IVIG demonstrated high VWF:Ag and low ADAMTS13:AC at Pre, and high VWF:Ag/ADAMTS13:AC ratio at 1 W compared to responders, but there were no significant differences in VWFM distribution between both groups. IEF analyses revealed the decreased free form of ADAMTS13 and increased complex form with ADAMTS13 and high-molecular-weight-VWFM at Pre in non-responders. A high VWF:Ag/ADAMTS13:AC ratio was associated with increased white blood cell counts, together with decreased serum albumin and sodium at Pre and 1 W. CONCLUSIONS: A high VWF:Ag/ADAMTS13:AC ratio in acute-KD persisted after primary treatment in non-responders, and unbalanced substrate-to-enzyme ratio appeared to associate with vascular endothelial damage. Analysis of existing mode of ADAMTS13 may help to clarify pathogenesis of IVIG resistance in acute-KD.

Blood group antigen A on von Willebrand factor is more protective against ADAMTS13 cleavage than antigens B and H.

BACKGROUND: ADAMTS13 specifically cleaves the peptide bond between Y1605 and M1606 within the VWF-A2 domain. OBJECTIVE: The VWF contains ABO(H) blood group antigens, which may influence the susceptibility of VWF to ADAMTS13. METHODS: Using a unique monoclonal antibody recognizing the Y1605 residue, we have developed a sandwich ELISA to analyze the generation of a VWF-DP by ADAMTS13 quantitatively. RESULTS: Production of VWF-DP after exposure to four different degrees of high shear stress was validated in comparison to the reduction in high-molecular-weight multimers using VWF multimer analysis. In analysis of plasma from 259 healthy individuals, plasma levels of VWF antigen (VWF:Ag) were significantly lower in blood group O than in the other groups and were significantly correlated with plasma VWF-DP levels. The ratio between VWF-DP and VWF:Ag was significantly higher in blood group O than in blood groups A and AB. The ratio in blood group B was also significantly higher than those in A and AB, but did not differ from blood group O. Finally, to examine whether ABO(H) blood group antigens contributed to VWF cleavage, 82 plasma samples were exposed to high shear stress using a cone-plate shear stress inducer. The difference in the VWF-DP/VWF:Ag ratio before and after high shear stress in blood group O was significantly greater than those in groups A and AB. CONCLUSION: These results indicate that blood group antigen A on VWF was more protective against ADAMTS13 cleavage than antigens B and H.

Thrombotic microangiopathy in a very young infant with mitral valvuloplasty.

BACKGROUND: Thrombotic microangiopathies (TMA) are microvascular occlusive disorders characterized by systemic or intrarenal platelet aggregation, thrombocytopenia, and red cell fragmentation. Post-operative TMA mostly occurs in adult patients with cardiovascular surgery, with the distinct pathophysiology from classical thrombotic thrombocytopenic purpura (TTP) although the exact pathophysiology remains unclear. CASE PRESENTATION: A one-month-old infant developed TMA after the initial surgery of double outlet right ventricle. ADAM metallopeptidase with thrombospondin type 1 motif 13 (ADAMTS13) activity was sustained (64%) with the undetectable inhibitor. Von Willebrand factor (VWF) multimer analyses showed absent high-molecular weight multimers. Echocardiography disclosed severe mitral regurgitation. The mitral valve repair 32 days after the initial valvuloplasty led to prompt resolution of TMA. These suggested that TMA occurred in association with valvulopathy-triggered turbulent shear flow, mechanical hemolysis and endothelial damage. The consumption of large VWF multimers might account for the vascular high shear stress shown in Heyde syndrome. CONCLUSION: The youngest case of post-operative TMA underscores the critical coagulopathy after the first surgical intervention for congenital heart disease.

Secretion of GLP-1 but not GIP is potently stimulated by luminal d-Allulose (d-Psicose) in rats.

Glucagon-like peptide 1 (GLP-1), an incretin gastrointestinal hormone, is secreted when stimulated by nutrients including metabolizable sugars such as glucose and fructose. d-Allulose (allulose), also known as d-psicose, is a C-3 isomer of d-fructose and a rare sugar with anti-diabetic or anti-obese effects in animal models. In the present study, we examined whether an oral administration of allulose could stimulate GLP-1 secretion in rats, and investigated the underlying mechanisms. Oral, but not intraperitoneal, administration of allulose (0.5-2.0 g/kg body weight) elevated plasma GLP-1 levels for more than 2 h in a dose-dependent manner. The effects of allulose on GLP-1 secretion were higher than that of dextrin, fructose, or glucose. In addition, oral allulose increased total and active GLP-1, but not glucose-dependent insulinotropic polypeptide (GIP), levels in the portal vein. In anesthetized rats equipped with a portal catheter, luminal (duodenum and ileum) administration of allulose increased portal GLP-1 levels, indicating the luminal effect of allulose. Allulose-induced GLP-1 secretion was abolished in the presence of xanthohumol (a glucose/fructose transport inhibitor), but not in the presence of inhibitors of the sodium-dependent glucose cotransporter 1 or the sweet taste receptor. These results demonstrate a potent and lasting effect of orally administered allulose on GLP-1 secretion in rats, without affecting GIP secretion. The potent and selective GLP-1-releasing effect of allulose holds promise for the prevention and treatment of glucose intolerance through promoting endogenous GLP-1 secretion.