Diabetic cardiomyopathy (DCM) is a major cause of mortality/morbidity in diabetes mellitus patien... more Diabetic cardiomyopathy (DCM) is a major cause of mortality/morbidity in diabetes mellitus patients. Although tetrahydrobiopterin (BH4) shows therapeutic potential as an endogenous cardiovascular target, its effect on myocardial cells and mitochondria in DCM and the underlying mechanisms remain unknown. Here, we determined the involvement of BH4 deficiency in DCM and the therapeutic potential of BH4 supplementation in a rodent DCM model. We observed a decreased BH4:total biopterin ratio in heart and mitochondria accompanied by cardiac remodeling, lower cardiac contractility, and mitochondrial dysfunction. Prolonged BH4 supplementation improved cardiac function, corrected morphological abnormalities in cardiac muscle, and increased mitochondrial activity. Proteomics analysis revealed oxidative phosphorylation (OXPHOS) as the BH4-targeted biological pathway in diabetic hearts as well as BH4-mediated rescue of down-regulated peroxisome proliferator-activated receptor-γ coactivator 1-α ...
Background Frailty is a multifactorial physiological syndrome most often associated with age but ... more Background Frailty is a multifactorial physiological syndrome most often associated with age but which has received increasing recognition as a component of chronic illnesses such as heart failure. Patients with heart failure are likely to be frail, irrespective of their age. Adipokine dysregulation, which is associated with frailty, occurs in patients with heart failure. In this study, we tested the hypothesis that adipokines are associated with frailty in patients with heart failure. Methods Thirty-five patients with heart failure (age, 67 ± 14 years; 25 males; left ventricular ejection fraction, 45 ± 19%) were included. Serum adipokine levels, physical performance, and body composition were measured. Results Adiponectin and leptin were inversely correlated with grip strength. Adiponectin was inversely correlated with bone mineral density. Leptin was positively correlated with fat mass. Adipokines were not correlated with skeletal muscle mass. Conclusions Adipokines were associate...
Prognosis of severe heart failure remains poor. Urgent new therapies are required. Some heart fai... more Prognosis of severe heart failure remains poor. Urgent new therapies are required. Some heart failure patients do not respond to established multidisciplinary treatment and are classified as “non-responders”. The outcome is especially poor for non-responders, and underlying mechanisms are largely unknown. Mitofusin-1 (Mfn1), a mitochondrial fusion protein, is significantly reduced in non-responding patients. This study aimed to elucidate the role of Mfn1 in the failing heart. Twenty-two idiopathic dilated cardiomyopathy (IDCM) patients who underwent endomyocardial biopsy of intraventricular septum were included. Of the 22 patients, 8 were non-responders (left ventricular (LV) ejection fraction (LVEF) of
Patients with type 2 diabetes treated with Sodium glucose transporter 2 (SGLT2) inhibitors show r... more Patients with type 2 diabetes treated with Sodium glucose transporter 2 (SGLT2) inhibitors show reduced mortality and hospitalization for heart failure (HF). SGLT2 inhibitors are considered to activate multiple cardioprotective pathways; however, underlying mechanisms are not fully described. This study aimed to elucidate the underlying mechanisms of the beneficial effects of SGLT2 inhibitors on the failing heart. We generated a left ventricular (LV) pressure overload model in C57BL/6NCrSlc mice by transverse aortic constriction (TAC) and examined the effects of empagliflozin (EMPA) in this model. We conducted metabolome and transcriptome analyses and histological and physiological examinations. EMPA administration ameliorated pressure overload-induced systolic dysfunction. Metabolomic studies showed that EMPA increased citrulline levels in cardiac tissue and reduced levels of arginine, indicating enhanced metabolism from arginine to citrulline and nitric oxide (NO). Transcriptome s...
Endothelial cells have an important role in maintaining vascular homeostasis. Age-related disorde... more Endothelial cells have an important role in maintaining vascular homeostasis. Age-related disorders (including obesity, diabetes, and hypertension) or aging per se induce endothelial dysfunction that predisposes to the development of atherosclerosis. Polyphenols have been reported to suppress age-related endothelial cell disorders, but their role in vascular function is yet to be determined. We investigated the influence of boysenberry polyphenol on vascular health under metabolic stress in a murine model of dietary obesity. We found that administration of boysenberry polyphenol suppressed production of reactive oxygen species (ROS) and increased production of nitric oxide (NO) in the aorta. It has been reported that p53 induces cellular senescence and has a crucial role in age-related disorders, including heart failure and diabetes. Administration of boysenberry polyphenol significantly reduced the endothelial p53 level in the aorta and ameliorated endothelial cell dysfunction in i...
Brown adipose tissue (BAT) is a metabolically active organ that contributes to the maintenance of... more Brown adipose tissue (BAT) is a metabolically active organ that contributes to the maintenance of systemic metabolism. The sympathetic nervous system plays important roles in the homeostasis of BAT and promotes its browning and activation. However, the role of other neurotransmitters in BAT homeostasis remains largely unknown. Our metabolomic analyses reveal that gamma-aminobutyric acid (GABA) levels are increased in the interscapular BAT of mice with dietary obesity. We also found a significant increase in GABA-type B receptor subunit 1 (GABA-BR1) in the cell membranes of brown adipocytes of dietary obese mice. When administered to obese mice, GABA induces BAT dysfunction together with systemic metabolic disorder. Conversely, the genetic inactivation or inhibition of GABA-BR1 leads to the re-browning of BAT under conditions of metabolic stress and ameliorated systemic glucose intolerance. These results indicate that the constitutive activation of GABA/GABA-BR1 signaling in obesity ...
Vascular cells have a finite lifespan and eventually enter irreversible growth arrest called cell... more Vascular cells have a finite lifespan and eventually enter irreversible growth arrest called cellular senescence. We have previously suggested that vascular cell senescence contributes to the pathogenesis of human atherosclerosis. Amlodipine is a mixture of two enantiomers, one of which (S- enantiomer) has L-type channel blocking activity, while the other (R+ enantiomer) shows ~1000-fold weaker channel blocking activity than S- enantiomer and has other unknown effects. It has been reported that amlodipine inhibits the progression of atherosclerosis in humans, but the molecular mechanism of this beneficial effect remains unknown. Apolipoprotein E-deficient mice on a high-fat diet were treated with amlodipine, its R+ enantiomer or vehicle for eight weeks. Compared with vehicle treatment, both amlodipine and the R+ enantiomer significantly reduced the number of senescent vascular cells and inhibited plaque formation to a similar extent. Expression of the pro-inflammatory molecule inter...
Previous studies have suggested that cellular senescence plays a central role in the progression ... more Previous studies have suggested that cellular senescence plays a central role in the progression of pathologic changes in the failing heart. It is well known that the sympathetic nervous system is activated in patients with heart failure, and this change is associated with poor clinical outcomes. Sympathetic activation increases the levels of various catecholamines, such as epinephrine and norepinephrine, but the contribution of these catecholamines to cellular senescence associated with heart failure remains to be determined. We found that catecholamine infusion induced senescence of endothelial cells and bone marrow cells, and promoted cardiac dysfunction in mice. In C57BL/6NCr mice, the continuous infusion of isoproterenol-induced cardiac inflammation and cardiac dysfunction. Expression of p53, a master regulator of cellular senescence, was increased in the cardiac tissue and bone marrow cells of these mice. Suppression of cellular senescence by genetic deletion of p53 in endothe...
Dipeptidyl peptidase 4 inhibitors are used worldwide in the management of diabetes, but their rol... more Dipeptidyl peptidase 4 inhibitors are used worldwide in the management of diabetes, but their role in the prevention or treatment of cardiovascular disorders has yet to be defined. We found that linagliptin, a DPP-4 inhibitor, suppressed capillary rarefaction in the hearts of mice with dietary obesity. Metabolomic analysis performed with capillary electrophoresis/mass spectrometry (LC-MS/MS) showed that linagliptin promoted favorable metabolic remodeling in cardiac tissue, which was characterized by high levels of citrulline and creatine. DNA microarray analysis revealed that the cardiac tissue level of early growth response protein 1 (EGR-1), which activates angiogenesis, was significantly reduced in untreated mice with dietary obesity, while this decrease was inhibited by administration of linagliptin. Mature fibroblast growth factor 2 (FGF-2) has a putative truncation site for DPP-4 at the NH2-terminal, and LC-MS/MS showed that recombinant DPP-4 protein cleaved the NH2-terminal d...
Wnt signaling has diverse actions in cardiovascular development and disease processes. Secreted f... more Wnt signaling has diverse actions in cardiovascular development and disease processes. Secreted frizzled-related protein 5 (Sfrp5) has been shown to function as an extracellular inhibitor of non-canonical Wnt signaling that is expressed at relatively high levels in white adipose tissue. The aim of this study was to investigate the role of Sfrp5 in the heart under ischemic stress. Sfrp5 knock-out (KO) and wild type (WT) mice were subjected to ischemia/reperfusion (I/R). Whereas Sfrp5-KO mice exhibited no detectable phenotype compared to WT control at baseline, they displayed larger infarct sizes, enhanced cardiac myocyte apoptosis and diminished cardiac function following I/R. The ischemic lesions of Sfrp5-KO mice had greater infiltration of Wnt5a-positive macrophages and greater inflammatory cytokine and chemokine gene expression compared to WT mice. In bone marrow-derived macrophages, Wnt5a promoted JNK activation and increased inflammatory gene expression, whereas treatment with S...
Diabetic cardiomyopathy (DCM) is a major cause of mortality/morbidity in diabetes mellitus patien... more Diabetic cardiomyopathy (DCM) is a major cause of mortality/morbidity in diabetes mellitus patients. Although tetrahydrobiopterin (BH4) shows therapeutic potential as an endogenous cardiovascular target, its effect on myocardial cells and mitochondria in DCM and the underlying mechanisms remain unknown. Here, we determined the involvement of BH4 deficiency in DCM and the therapeutic potential of BH4 supplementation in a rodent DCM model. We observed a decreased BH4:total biopterin ratio in heart and mitochondria accompanied by cardiac remodeling, lower cardiac contractility, and mitochondrial dysfunction. Prolonged BH4 supplementation improved cardiac function, corrected morphological abnormalities in cardiac muscle, and increased mitochondrial activity. Proteomics analysis revealed oxidative phosphorylation (OXPHOS) as the BH4-targeted biological pathway in diabetic hearts as well as BH4-mediated rescue of down-regulated peroxisome proliferator-activated receptor-γ coactivator 1-α ...
Background Frailty is a multifactorial physiological syndrome most often associated with age but ... more Background Frailty is a multifactorial physiological syndrome most often associated with age but which has received increasing recognition as a component of chronic illnesses such as heart failure. Patients with heart failure are likely to be frail, irrespective of their age. Adipokine dysregulation, which is associated with frailty, occurs in patients with heart failure. In this study, we tested the hypothesis that adipokines are associated with frailty in patients with heart failure. Methods Thirty-five patients with heart failure (age, 67 ± 14 years; 25 males; left ventricular ejection fraction, 45 ± 19%) were included. Serum adipokine levels, physical performance, and body composition were measured. Results Adiponectin and leptin were inversely correlated with grip strength. Adiponectin was inversely correlated with bone mineral density. Leptin was positively correlated with fat mass. Adipokines were not correlated with skeletal muscle mass. Conclusions Adipokines were associate...
Prognosis of severe heart failure remains poor. Urgent new therapies are required. Some heart fai... more Prognosis of severe heart failure remains poor. Urgent new therapies are required. Some heart failure patients do not respond to established multidisciplinary treatment and are classified as “non-responders”. The outcome is especially poor for non-responders, and underlying mechanisms are largely unknown. Mitofusin-1 (Mfn1), a mitochondrial fusion protein, is significantly reduced in non-responding patients. This study aimed to elucidate the role of Mfn1 in the failing heart. Twenty-two idiopathic dilated cardiomyopathy (IDCM) patients who underwent endomyocardial biopsy of intraventricular septum were included. Of the 22 patients, 8 were non-responders (left ventricular (LV) ejection fraction (LVEF) of
Patients with type 2 diabetes treated with Sodium glucose transporter 2 (SGLT2) inhibitors show r... more Patients with type 2 diabetes treated with Sodium glucose transporter 2 (SGLT2) inhibitors show reduced mortality and hospitalization for heart failure (HF). SGLT2 inhibitors are considered to activate multiple cardioprotective pathways; however, underlying mechanisms are not fully described. This study aimed to elucidate the underlying mechanisms of the beneficial effects of SGLT2 inhibitors on the failing heart. We generated a left ventricular (LV) pressure overload model in C57BL/6NCrSlc mice by transverse aortic constriction (TAC) and examined the effects of empagliflozin (EMPA) in this model. We conducted metabolome and transcriptome analyses and histological and physiological examinations. EMPA administration ameliorated pressure overload-induced systolic dysfunction. Metabolomic studies showed that EMPA increased citrulline levels in cardiac tissue and reduced levels of arginine, indicating enhanced metabolism from arginine to citrulline and nitric oxide (NO). Transcriptome s...
Endothelial cells have an important role in maintaining vascular homeostasis. Age-related disorde... more Endothelial cells have an important role in maintaining vascular homeostasis. Age-related disorders (including obesity, diabetes, and hypertension) or aging per se induce endothelial dysfunction that predisposes to the development of atherosclerosis. Polyphenols have been reported to suppress age-related endothelial cell disorders, but their role in vascular function is yet to be determined. We investigated the influence of boysenberry polyphenol on vascular health under metabolic stress in a murine model of dietary obesity. We found that administration of boysenberry polyphenol suppressed production of reactive oxygen species (ROS) and increased production of nitric oxide (NO) in the aorta. It has been reported that p53 induces cellular senescence and has a crucial role in age-related disorders, including heart failure and diabetes. Administration of boysenberry polyphenol significantly reduced the endothelial p53 level in the aorta and ameliorated endothelial cell dysfunction in i...
Brown adipose tissue (BAT) is a metabolically active organ that contributes to the maintenance of... more Brown adipose tissue (BAT) is a metabolically active organ that contributes to the maintenance of systemic metabolism. The sympathetic nervous system plays important roles in the homeostasis of BAT and promotes its browning and activation. However, the role of other neurotransmitters in BAT homeostasis remains largely unknown. Our metabolomic analyses reveal that gamma-aminobutyric acid (GABA) levels are increased in the interscapular BAT of mice with dietary obesity. We also found a significant increase in GABA-type B receptor subunit 1 (GABA-BR1) in the cell membranes of brown adipocytes of dietary obese mice. When administered to obese mice, GABA induces BAT dysfunction together with systemic metabolic disorder. Conversely, the genetic inactivation or inhibition of GABA-BR1 leads to the re-browning of BAT under conditions of metabolic stress and ameliorated systemic glucose intolerance. These results indicate that the constitutive activation of GABA/GABA-BR1 signaling in obesity ...
Vascular cells have a finite lifespan and eventually enter irreversible growth arrest called cell... more Vascular cells have a finite lifespan and eventually enter irreversible growth arrest called cellular senescence. We have previously suggested that vascular cell senescence contributes to the pathogenesis of human atherosclerosis. Amlodipine is a mixture of two enantiomers, one of which (S- enantiomer) has L-type channel blocking activity, while the other (R+ enantiomer) shows ~1000-fold weaker channel blocking activity than S- enantiomer and has other unknown effects. It has been reported that amlodipine inhibits the progression of atherosclerosis in humans, but the molecular mechanism of this beneficial effect remains unknown. Apolipoprotein E-deficient mice on a high-fat diet were treated with amlodipine, its R+ enantiomer or vehicle for eight weeks. Compared with vehicle treatment, both amlodipine and the R+ enantiomer significantly reduced the number of senescent vascular cells and inhibited plaque formation to a similar extent. Expression of the pro-inflammatory molecule inter...
Previous studies have suggested that cellular senescence plays a central role in the progression ... more Previous studies have suggested that cellular senescence plays a central role in the progression of pathologic changes in the failing heart. It is well known that the sympathetic nervous system is activated in patients with heart failure, and this change is associated with poor clinical outcomes. Sympathetic activation increases the levels of various catecholamines, such as epinephrine and norepinephrine, but the contribution of these catecholamines to cellular senescence associated with heart failure remains to be determined. We found that catecholamine infusion induced senescence of endothelial cells and bone marrow cells, and promoted cardiac dysfunction in mice. In C57BL/6NCr mice, the continuous infusion of isoproterenol-induced cardiac inflammation and cardiac dysfunction. Expression of p53, a master regulator of cellular senescence, was increased in the cardiac tissue and bone marrow cells of these mice. Suppression of cellular senescence by genetic deletion of p53 in endothe...
Dipeptidyl peptidase 4 inhibitors are used worldwide in the management of diabetes, but their rol... more Dipeptidyl peptidase 4 inhibitors are used worldwide in the management of diabetes, but their role in the prevention or treatment of cardiovascular disorders has yet to be defined. We found that linagliptin, a DPP-4 inhibitor, suppressed capillary rarefaction in the hearts of mice with dietary obesity. Metabolomic analysis performed with capillary electrophoresis/mass spectrometry (LC-MS/MS) showed that linagliptin promoted favorable metabolic remodeling in cardiac tissue, which was characterized by high levels of citrulline and creatine. DNA microarray analysis revealed that the cardiac tissue level of early growth response protein 1 (EGR-1), which activates angiogenesis, was significantly reduced in untreated mice with dietary obesity, while this decrease was inhibited by administration of linagliptin. Mature fibroblast growth factor 2 (FGF-2) has a putative truncation site for DPP-4 at the NH2-terminal, and LC-MS/MS showed that recombinant DPP-4 protein cleaved the NH2-terminal d...
Wnt signaling has diverse actions in cardiovascular development and disease processes. Secreted f... more Wnt signaling has diverse actions in cardiovascular development and disease processes. Secreted frizzled-related protein 5 (Sfrp5) has been shown to function as an extracellular inhibitor of non-canonical Wnt signaling that is expressed at relatively high levels in white adipose tissue. The aim of this study was to investigate the role of Sfrp5 in the heart under ischemic stress. Sfrp5 knock-out (KO) and wild type (WT) mice were subjected to ischemia/reperfusion (I/R). Whereas Sfrp5-KO mice exhibited no detectable phenotype compared to WT control at baseline, they displayed larger infarct sizes, enhanced cardiac myocyte apoptosis and diminished cardiac function following I/R. The ischemic lesions of Sfrp5-KO mice had greater infiltration of Wnt5a-positive macrophages and greater inflammatory cytokine and chemokine gene expression compared to WT mice. In bone marrow-derived macrophages, Wnt5a promoted JNK activation and increased inflammatory gene expression, whereas treatment with S...
Uploads
Papers by Ippei Shimizu