Succinyl-CoA-based energy metabolism dysfunction in chronic heart failure.

Heart failure (HF) is a leading cause of death and repeated hospitalizations and often involves cardiac mitochondrial dysfunction. However, the underlying mechanisms largely remain elusive. Here, using a mouse model in which myocardial infarction (MI) was induced by coronary artery ligation, we show the metabolic basis of mitochondrial dysfunction in chronic HF. Four weeks after ligation, MI mice showed a significant decrease in myocardial succinyl-CoA levels, and this decrease impaired the mitochondrial oxidative phosphorylation (OXPHOS) capacity. Heme synthesis and ketolysis, and protein levels of several enzymes consuming succinyl-CoA in these events, were increased in MI mice, while enzymes synthesizing succinyl-CoA from α-ketoglutarate and glutamate were also increased. Furthermore, the ADP-specific subunit of succinyl-CoA synthase was reduced, while its GDP-specific subunit was almost unchanged. Administration of 5-aminolevulinic acid, an intermediate in the pathway from succinyl-CoA to heme synthesis, appreciably restored succinyl-CoA levels and OXPHOS capacity and prevented HF progression in MI mice. Previous reports also suggested the presence of succinyl-CoA metabolism abnormalities in cardiac muscles of HF patients. Our results identified that changes in succinyl-CoA usage in different metabolisms of the mitochondrial energy production system is characteristic to chronic HF, and although similar alterations are known to occur in healthy conditions, such as during strenuous exercise, they may often occur irreversibly in chronic HF leading to a decrease in succinyl-CoA. Consequently, nutritional interventions compensating the succinyl-CoA consumption are expected to be promising strategies to treat HF.

Angiotensin-converting enzyme inhibitor prevents skeletal muscle fibrosis in diabetic mice.

NEW FINDINGS: What is the central question of this study? We questioned whether an angiotensin-converting enzyme (ACE) inhibitor prevents skeletal muscle fibrosis in diabetic mice. What is the main finding and its importance? Administration of ACE inhibitor prevents the increase in skeletal muscle fibrosis during the early phase after induction of diabetes by streptozotocin. Our findings might provide a new therapeutic target for skeletal muscle abnormalities in diabetes. ABSTRACT: Fibrosis is characterized by the excessive production and accumulation of extracellular matrix components, including collagen. Although the extracellular matrix is an essential component of skeletal muscle, fibrosis can have negative effects on muscle function. Skeletal muscle fibrosis was shown to be increased in spontaneously hypertensive rats and to be prevented by an angiotensin-converting enzyme (ACE) inhibitor, an antihypertensive drug, in dystrophic mice or a mouse model of myocardial infarction. In this study, we therefore analysed whether (1) there is increased skeletal muscle fibrosis in streptozotocin (STZ)-induced diabetic mice, and (2) a preventive effect on skeletal muscle fibrosis by administration of an ACE inhibitor. Skeletal muscle fibrosis was significantly increased in STZ-induced diabetic mice compared with control mice from 2 to 14 days post-STZ. The ACE inhibitor prevented both skeletal muscle fibrosis and the reduction in muscle function in STZ-treated mice. Our study demonstrated that administration of an ACE inhibitor prevents the increase in skeletal muscle fibrosis during the early phase after onset of diabetes. Our findings might provide a new therapeutic target for skeletal muscle abnormalities in diabetes. Future studies are required to clarify whether skeletal muscle fibrosis is also linked directly to physical activity.

Enhanced Echo Intensity of Skeletal Muscle Is Associated With Exercise Intolerance in Patients With Heart Failure.

BACKGROUND: Skeletal muscle is quantitatively and qualitatively impaired in patients with heart failure (HF), which is closely linked to lowered exercise capacity. Ultrasonography (US) for skeletal muscle has emerged as a useful, noninvasive tool to evaluate muscle quality and quantity. Here we investigated whether muscle quality based on US-derived echo intensity (EI) is associated with exercise capacity in patients with HF. METHODS AND RESULTS: Fifty-eight patients with HF (61 ± 12 years) and 28 control subjects (58 ± 14 years) were studied. The quadriceps femoris echo intensity (QEI) was significantly higher and the quadriceps femoris muscle thickness (QMT) was significantly lower in the patients with HF than the controls (88.3 ± 13.4 vs 81.1 ± 7.5, P= .010; 5.21 ± 1.10 vs 6.54 ±1.34 cm, P< .001, respectively). By univariate analysis, QEI was significantly correlated with age, peak oxygen uptake (VO2), and New York Heart Association class in the HF group. A multivariable analysis revealed that the QEI was independently associated with peak VO2 after adjustment for age, gender, body mass index, and QMT: ß-coefficient = -11.80, 95%CI (-20.73, -2.86), P= .011. CONCLUSION: Enhanced EI in skeletal muscle was independently associated with lowered exercise capacity in HF. The measurement of EI is low-cost, easily accessible, and suitable for assessment of HF-related alterations in skeletal muscle quality.

Type 2 diabetes is an independent predictor of lowered peak aerobic capacity in heart failure patients with non-reduced or reduced left ventricular ejection fraction.

BACKGROUND: Although type 2 diabetes mellitus (T2DM) is one of the most frequent comorbidities in patients with chronic heart failure (CHF), the effects of T2DM on the exercise capacity of CHF patients are fully unknown. Here, we tested the hypothesis that the coexistence of T2DM lowers CHF patients' peak aerobic capacity. METHODS: We retrospectively analyzed the cases of 275 Japanese CHF patients with non-reduced ejection fraction (left ventricular ejection fraction [LVEF] ≥ 40%) or reduced EF (LVEF < 40%) who underwent cardiopulmonary exercise testing. We divided them into diabetic and nondiabetic groups in each CHF cohort. RESULTS: The mean peak oxygen uptake (VO2) value was 16.87 mL/kg/min in the non-reduced LVEF cohort and 15.52 mL/kg/min in the reduced LVEF cohort. The peak VO2 was lower in the diabetics versus the nondiabetics in the non-reduced LVEF cohort with the mean difference (95% confidence interval [95% CI]) of - 0.93 (- 1.82 to - 0.04) mL/kg/min and in the reduced LVEF cohort with the mean difference of - 1.05 (- 1.96 to - 0.15) mL/kg/min, after adjustment for age-squared, gender, anemia, renal function, LVEF, and log B-type natriuretic peptide (BNP). The adjusted VO2 at anaerobic threshold (AT), a submaximal aerobic capacity, was also decreased in the diabetic patients with both non-reduced and reduced LVEFs. Intriguingly, the diabetic patients had a lower adjusted peak O2 pulse than the nondiabetic patients in the reduced LVEF cohort, but not in the non-reduced LVEF cohort. A multivariate analysis showed that the presence of T2DM was an independent predictor of lowered peak VO2 in CHF patients with non-reduced LVEF and those with reduced LVEF. CONCLUSIONS: T2DM was associated with lowered peak VO2 in CHF patients with non-reduced or reduced LVEF. The presence of T2DM has a negative impact on CHF patients' exercise capacity, and the degree of impact is partly dependent on their LV systolic function.

The disruption of invariant natural killer T cells exacerbates cardiac hypertrophy and failure caused by pressure overload in mice.

NEW FINDINGS: What is the central question of this study? We questioned whether the disruption of invariant natural killer T (iNKT) cells exacerbates left ventricular (LV) remodelling and heart failure after transverse aortic constriction in mice. What are the main findings and their importance? Pressure overload induced by transverse aortic constriction increased the infiltration of iNKT cells in mouse hearts. The disruption of iNKT cells exacerbated LV remodelling and hastened the transition from hypertrophy to heart failure, in association with the activation of mitogen-activated protein kinase signalling. Activation of iNKT cells modulated the immunological balance in this process and played a protective role against LV remodelling and failure. ABSTRACT: Chronic inflammation is involved in the development of cardiac remodelling and heart failure (HF). Invariant natural killer T (iNKT) cells, a subset of T lymphocytes, have been shown to produce various cytokines and orchestrate tissue inflammation. The pathophysiological role of iNKT cells in HF caused by pressure overload has not been studied. In the present study, we investigated whether the disruption of iNKT cells affected this process in mice. Transverse aortic constriction (TAC) and a sham operation were performed in male C57BL/6J wild-type (WT) and iNKT cell-deficient Jα18 knockout (KO) mice. The infiltration of iNKT cells was increased after TAC. The disruption of iNKT cells exacerbated left ventricular (LV) remodelling and hastened the transition to HF after TAC. Histological examinations also revealed that the disruption of iNKT cells induced greater myocyte hypertrophy and a greater increase in interstitial fibrosis after TAC. The expressions of interleukin-10 and tumour necrosis factor-α mRNA and their ratio in the LV after TAC were decreased in the KO compared with WT mice, which might indicate that the disruption of iNKT cells leads to an imbalance between T-helper type 1 and type 2 cytokines. The phosphorylation of extracellular signal-regulated kinase was significantly increased in the KO mice. The disruption of iNKT cells exacerbated the development of cardiac remodelling and HF after TAC. The activation of iNKT cells might play a protective role against HF caused by pressure overload. Targeting the activation of iNKT cells might thus be a promising candidate as a new therapeutic strategy for HF.

Serum Brain-Derived Neurotrophic Factor Levels Are Associated with Skeletal Muscle Function but Not with Muscle Mass in Patients with Heart Failure.

Heart failure (HF) is associated with aberrant skeletal muscle impairments, which are closely linked to the severity of HF. A low level of brain-derived neurotrophic factor (BDNF), a myokine produced in the skeletal muscle, is known to be involved in reduced exercise capacity and poor prognosis in HF. However, little is known about the factors or conditions of skeletal muscle associated with BDNF levels. We investigated the association between serum BDNF levels and the skeletal muscle mass and function in HF patients (n = 60, 63 ± 13 years) and age-matched controls (n = 29, 61 ± 16 years). The serum BDNF level was significantly lower in the HF patients compared to the controls (24.9 ± 0.9 versus 28.6 ± 1.3, P = 0.021). In a univariate analysis, BDNF was significantly correlated with the peak oxygen uptake, estimated glomerular filtration rate, 10-m gait speed, and muscle strength, but not with the body mass index or lean mass in the HF group. A multiple linear regression analysis revealed that BDNF was independently associated with muscle strength (ß-coefficient = 2.80, 95%CI: 1.89-11.8, P = 0.008). Serum BDNF levels were associated with exercise capacity and skeletal muscle function, but not with muscle mass. These novel findings may suggest that BDNF production is controlled by muscle function and activity and consequently regulates exercise capacity, highlighting the importance of adequate training regarding skeletal muscle in HF patients.

[Development of an LC-MS/MS-Based Rapid and Simple Analytical Method for Six Fungicides].

In this study, we developed an LC-MS/MS-based rapid and simple analytical method for six fungicides; imazalil, o-phenylphenol, thiabendazole, fludioxonil, azoxystrobin and pyrimethanil, the latter three were newly approved for use after 2011. For expediting and simplification, we merged the extraction method with that of the pesticide analysis. For purification step, loading of 1 mL of sample extracts to 500 mg Oasis HLB column and elution with 8 mL of acetonitrile gave satisfactory results. The performance of the present method was confirmed for orange, grapefruit, and lemon samples fortified with the six fungicides. The results showed that the average recovery ranged from 89.7 to 100.0%, intra- and inter-assay CV% ranged from 1.5 to 5.0% and from 0.5 to 4.9%, respectively, achieving the target values of the Japanese official guideline for residual pesticide analysis. The limits of quantification of this method were determined to be 1 mg/kg for o-phenylphenol, and 0.2 mg/kg for the other five fungicides. These values were lower than their corresponding regulation values. In addition, we confirmed the usability of the present method for fungicide inspection of commercially available citrus fruits. During 2017-2019, there was no conflict between the food labeling and the fungicides detected and no fungicide with the concentration exceeding maximum residue level was detected.

Linoleic acid improves assembly of the CII subunit and CIII2/CIV complex of the mitochondrial oxidative phosphorylation system in heart failure.

BACKGROUND: Linoleic acid is the major fatty acid moiety of cardiolipin, which is central to the assembly of components involved in mitochondrial oxidative phosphorylation (OXPHOS). Although linoleic acid is an essential nutrient, its excess intake is harmful to health. On the other hand, linoleic acid has been shown to prevent the reduction in cardiolipin content and to improve mitochondrial function in aged rats with spontaneous hypertensive heart failure (HF). In this study, we found that lower dietary intake of linoleic acid in HF patients statistically correlates with greater severity of HF, and we investigated the mechanisms therein involved. METHODS: HF patients, who were classified as New York Heart Association (NYHA) functional class I (n = 45), II (n = 93), and III (n = 15), were analyzed regarding their dietary intakes of different fatty acids during the one month prior to the study. Then, using a mouse model of HF, we confirmed reduced cardiolipin levels in their cardiac myocytes, and then analyzed the mechanisms by which dietary supplementation of linoleic acid improves cardiac malfunction of mitochondria. RESULTS: The dietary intake of linoleic acid was significantly lower in NYHA III patients, as compared to NYHA II patients. In HF model mice, both CI-based and CII-based OXPHOS activities were affected together with reduced cardiolipin levels. Silencing of CRLS1, which encodes cardiolipin synthetase, in cultured cardiomyocytes phenocopied these events. Feeding HF mice with linoleic acid improved both CI-based and CII-based respiration as well as left ventricular function, together with an increase in cardiolipin levels. However, although assembly of the respirasome (i.e., CI/CIII2/CIV complex), as well as assembly of CII subunits and the CIII2/CIV complex statistically correlated with cardiolipin levels in cultured cardiomyocytes, respirasome assembly was not notably restored by dietary linoleic acid in HF mice. Therefore, although linoleic acid may significantly improve both CI-based and CII-based respiration of cardiomyocytes, respirasomes impaired by HF were not easily repaired by the dietary intake of linoleic acid. CONCLUSIONS: Dietary supplement of linoleic acid is beneficial for improving cardiac malfunction in HF, but is unable to completely cure HF.

Inhomogeneity of sediment samples in analysis of hexabromocyclododecane.

The repeatability test of the analytical method for hexabromocyclododecane (HBCD) was conducted with sediment sample. The maximum HBCD concentration exceeded the minimum by a factor of 90 even though the identical sediment samples were used. Therefore, we examined which step of the analytical method was the factor causing variability. We examined the blank test, and confirmation test of the extraction and purified procedure. From these results, we confirmed that there was nothing wrong with the accuracy of our analytical method. These results indicate that the variability of HBCD concentration in the repeatability test was attributed not to the analytical method, but to the inhomogeneity of the sediment sample. Aluminum, silicon, and organic carbon in sediments were measured to compare the variability of these concentrations with that of HBCD concentration. These concentrations were similar values within identical samples which showed variability in HBCD concentration. HBCD concentration in several samples did not correlate with organic carbon content. These results suggests that sediment samples were homogeneous by itself, and HBCD was heterogeneously distributed in spite of homogeneity of organic carbon in sediment. The sediment sample with variability in HBCD concentration showed different HBCD diastereomer compositions in identical sediment. It implies that the sample contained HBCD derived from different histories or point sources. Even though we increased sample amounts to analyze the homogeneity of the sample, HBCD concentration varied within identical samples if the sample had a hot spot. Past monitoring data may contain overestimation or underestimation of HBCD concentration in sediment.

[Headspace GC/MS Analysis of Residual Solvents in Laminated Films Used for Food Packaging].

Multilayer laminated films may contain organic solvents derived from adhesives, printing inks and so on. A headspace-GC/MS analysis method for the simultaneous determination of 30 substances such as toluene, xylene, acetone, methyl ethyl ketone, ethyl acetate, butyl acetate, methanol, ethanol, was developed. A N,N-dimethyl formamide solution containing an internal standard substance was added to the sample. After leaving overnight at room temperature, the headspace gas was analyzed by GC/MS. This method was applicable to a laminate film made of various materials. The organic solvents such as toluene, ethyl acetate, and heptane were detected from 6 out of 42 food packaging bags made from laminated film on Japanese market using this method.

Small-conductance Ca2+-activated K+ channel activation deteriorates hypoxic ventricular arrhythmias via CaMKII in cardiac hypertrophy.

The molecular and electrophysiological mechanisms of acute ischemic ventricular arrhythmias in hypertrophied hearts are not well known. We hypothesized that small-conductance Ca2+-activated K+ (SK) channels are activated during hypoxia via the Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent pathway. We used normotensive Wistar-Kyoto (WKY) rats and spontaneous hypertensive rats (SHRs) as a model of cardiac hypertrophy. The inhibitory effects of SK channels and ATP-sensitive K+ channels on electrophysiological changes and genesis of arrhythmias during simulated global hypoxia (GH) were evaluated. Hypoxia-induced abbreviation of action potential duration (APD) occurred earlier in ventricles from SHRs versus. WKY rats. Apamin, a SK channel blocker, prevented this abbreviation in SHRs in both the early and delayed phase of GH, whereas in WKY rats only the delayed phase was prevented. In contrast, SHRs were less sensitive to glibenclamide, a ATP-sensitive K+ channel blocker, which inhibited the APD abbreviation in both phases of GH in WKY rats. SK channel blockers (apamin and UCL-1684) reduced the incidence of hypoxia-induced sustained ventricular arrhythmias in SHRs but not in WKY rats. Among three SK channel isoforms, SK2 channels were directly coimmunoprecipitated with CaMKII phosphorylated at Thr286 (p-CaMKII). We conclude that activation of SK channels leads to the APD abbreviation and sustained ventricular arrhythmias during simulated hypoxia, especially in hypertrophied hearts. This mechanism may result from p-CaMKII-bound SK2 channels and reveal new molecular targets to prevent lethal ventricular arrhythmias during acute hypoxia in cardiac hypertrophy. NEW & NOTEWORTHY We now show a new pathophysiological role of small-conductance Ca2+-activated K+ channels, which shorten the action potential duration and induce ventricular arrhythmias during hypoxia. We also demonstrate that small-conductance Ca2+-activated K+ channels interact with phosphorylated Ca2+/calmodulin-dependent protein kinase II at Thr286 in hypertrophied hearts.

Impact of High Respiratory Exchange Ratio During Submaximal Exercise on Adverse Clinical Outcome in Heart Failure.

BACKGROUND: Oxygen uptake (V̇O2) at peak workload and anaerobic threshold (AT) workload are often used for grading heart failure (HF) severity and predicting all-cause mortality. The clinical relevance of respiratory exchange ratio (RER) during exercise, however, is unknown. Methods and Results: We retrospectively studied 295 HF patients (57±15 years, NYHA class I-III) who underwent cardiopulmonary exercise testing. RER was measured at rest; at AT workload; and at peak workload. Peak V̇O2 had an inverse correlation with RER at AT workload (r=-0.256), but not at rest (r=-0.084) or at peak workload (r=0.090). Using median RER at AT workload, we divided the patients into high RER (≥0.97) and low RER (<0.97) groups. Patients with high RER at AT workload were characterized by older age, lower body mass index, anemia, and advanced NYHA class. After propensity score matching, peak V̇O2 tended to be lower in the high-RER than in the low-RER group (14.9±4.5 vs. 16.1±5.0 mL/kg/min, P=0.06). On Kaplan-Meier analysis, HF patients with a high RER at AT workload had significantly worse clinical outcomes, including all-cause mortality and rate of readmission due to HF worsening over 3 years (29% vs. 15%, P=0.01). CONCLUSIONS: High RER during submaximal exercise, particularly at AT workload, is associated with poor clinical outcome in HF patients.

[Enhancement of Pesticide Peak Response in GC-MS in the Presence of Multiple Co-Existing Reference Pesticides].

We carried out a collaborative study in six laboratories to confirm the universality of the enhancing effect of co-existing reference pesticides on the GC-MS peak response to a target pesticide (malathion, procymidone, or flucythrinate). First, we confirmed the response enhancement of the target pesticides with increasing numbers of co-existing reference pesticides in solution. Then, using diluted green soybean matrix, we analyzed the target pesticides with two types of matrix-matched calibration, containing the target pesticides or 166 other pesticides. In both cases, the response-enhancing effect of co-existing pesticides was confirmed in all laboratories. The enhancement was reduced by addition of green soybean matrix to the sample and calibration solutions. Our results show that it is necessary to estimate the peak response-enhancing effect of co-existing pesticides in the calibration solution to obtain accurate results with GC-MS determination. The enhancing effect could be reduced by addition of food matrix to the sample and calibration solutions.

[Analysis of Flame Retardants Bis(2,3-dibromopropyl) phosphate and Tris(2,3-dibromopropyl) phosphate in Textile Products by GC-MS].

The use of flame retardants, namely bis(2,3-dibromopropyl) phosphate (BDBPP) and tris(2,3-dibromopropyl) phosphate (TDBPP), in textile products such as curtains, carpets and sleeping clothes is banned in Japan under the 'Act on the Control of Household Products Containing Harmful Substances'. Herein, we developed a GC-MS based method to quantify these compounds with greater accuracy and safety than the current official method. For accurate and sensitive quantification, deuterated compounds, BDBPP-d10 and TDBPP-d15, were used as surrogate standards. In consideration of the safety of the analyst, certain solvents and reagents used for the pretreatment that are carcinogenic or have a risk of explosion were replaced. For the extraction step, benzene was replaced by ethyl acetate, and for the methyl derivatization step, the reagent was changed from a self-prepared solution of diazomethane in ether to a solution of trimethylsilyl diazomethane in hexane, a safe and easy-to-use commercially available reagent. The calibration curves were liner in the range of 0.5-8.0 µg/mL for both methylated BDBPP (BDBPP-Me) and TDBPP. The detection limit was 0.05 µg/g for BDBPP-Me and 0.3 µg/g for TDBPP, which is sufficiently low compared to the current detection limits of 10 µg/g for BDBPP-Me and 8 µg/g for TDBPP. The recoveries in various curtain material were 66-108% and relative standard deviations were 1.2-10.2% when 5 µg BDBPP and TDBPP were added to 0.5 g of samples. Thus, the developed method is applicable to textile products of various materials.

Determination of potential volatile compounds in polyethylene terephthalate (PET) bottles and their short- and long-term migration into food simulants and soft drink.

Head space (HS)-GC-MS was used to analyze possible migration of volatile compounds from polyethylene terephthalate (PET) bottles for soft drinks, and a total of six compounds were identified. Next, a rapid, simple, and accurate simultaneous method was established using purge-and-trap (PT)-GC-MS, to quantify their amounts in the liquid contents after short- and long-term storage in PET bottles. Starting with brand-new PET bottles, the maximum migration of 2-methyl-1,3-dioxolane into distilled water and 50 % aqueous ethanol after 2 years at 25 °C were 2.3 and 19 ng/mL, respectively. In commercially available bottled mineral water sold inside and outside Japan, we were able to detect 2-methyl-1,3-dioxolane in the same way. While nonanal was also detected in some products, 2-methyl-1,3-dioxolane was confirmed as the main volatile compound. Finally, the human exposure to 2-methyl-1,3-dioxolane was estimated based on the per capita intake of soft drinks in Japan and the migration amount in this study.

Impact of citrus fruit intake on the mental health of patients with chronic heart failure.

BACKGROUND: The full impact of the intake of citrus fruits on the risk of depression in individuals with chronic heart failure (HF) is unknown. Here, we examined the associations between the estimated habitual intakes of citrus fruits and depressive symptoms in patients with chronic HF. METHODS: We enrolled 150 stable outpatients with chronic HF who had a history of worsening HF. To assess the patients' daily dietary patterns, we used a brief self-administered diet-history questionnaire to calculate the daily consumption of foods and nutrients. To assess the patients' mental state, we used a nine-item Patient Health Questionnaire (PHQ-9). RESULTS: Twelve patients (8%) were identified as having moderate-to-severe depression (PHQ-9 score ≥10). The patients with PHQ-9 ≥10 had lower daily intakes of citrus fruits compared to those with no or mild depressive symptoms (PHQ-9 <10). The daily intakes of various antioxidants, including vitamin C, ß-carotene, and ß-cryptoxanthin, all of which are abundant in citrus fruits, were reduced in the patients with PHQ-9 ≥10, accompanied by higher serum levels of 8-isoprostane (an oxidative stress marker). A multivariate logistic regression analysis using forward selection showed that a lowered daily intake of citrus fruits was an independent predictor of the comorbidity of moderate-to-severe depression in patients with chronic HF, after adjustment for age, gender, and the hemoglobin value. CONCLUSIONS: A lower daily consumption of citrus fruits was associated with higher prevalence of depression in patients with chronic HF. Our findings support the hypothesis that a daily consumption of citrus fruits has a beneficial effect on the prevention and treatment of depression in chronic HF patients.

Comparison between mouse bioassay and HILIC-MS/MS for quantification of paralytic shellfish toxin in Japanese basket clams and mussels caught off coastal Osaka Bay in Japan.

The content and composition of paralytic shellfish toxins (PSTs) in Japanese basket clam (Corbicula japonica) and mussels (Mytilus galloprovincialis) from Osaka Bay, Japan, were investigated using a mouse bioassay (MBA) and hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS), and the association between toxicity values of MBA and HILIC-MS/MS was verified based on research data. The overall toxicity in Japanese basket clam was lower than that in the mussel. The PSTs of Japanese basket clam and mussel consisted mainly of C1, C2, and gonyautoxins 1-4 (GTX1-4) taking toxins compositional differences as mol%. When multiplying the content of different toxins by the toxic equivalent factor (TEF), C2 and GTX1-4 accounted for more than 90% of total toxicity (MU TEF/g) based on the MU TEF score converted by TEF for the two species. The total content of C2 and GTX1-4 converted to toxicity was significantly correlated with the toxicity determined by MBA for the two species (r2 > 0.983). This study provides a suitable and ethical monitoring method to investigate toxicity in bivalves contaminated with A. tamarense by analysis of only predominant toxins, along with reducing use of MBA.