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 ...
Prognosis of heart failure remains poor, and it is urgent to find new therapies for this critical... more Prognosis of heart failure remains poor, and it is urgent to find new therapies for this critical condition. Oxygen and metabolites are delivered through capillaries; therefore, they have critical roles in the maintenance of cardiac function. With aging or age-related disorders, capillary density is reduced in the heart, and the mechanisms involved in these processes were reported to suppress capillarization in this organ. Studies with rodents showed capillary rarefaction has causal roles for promoting pathologies in failing hearts. Drugs used as first-line therapies for heart failure were also shown to enhance the capillary network in the heart. Recently, the approach with senolysis is attracting enthusiasm in aging research. Genetic or pharmacological approaches concluded that the specific depletion of senescent cells, senolysis, led to reverse aging phenotype. Reagents mediating senolysis are described to be senolytics, and these compounds were shown to ameliorate cardiac dysfunction together with enhancement of capillarization in heart failure models. Studies indicate maintenance of the capillary network as critical for inhibition of pathologies in heart failure.
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...
Cell-proliferation potency is limited, as cells cannot proceed through the cell cycle continually... more Cell-proliferation potency is limited, as cells cannot proceed through the cell cycle continually. Instead, they eventually show an irreversible arrest of proliferation, commonly referred to as cellular senescence. Following the initial discovery of this phenomenon by Hayflick et al., studies have indicated that cells are also destined to undergo aging. In addition to the irreversible termination of proliferation, senescent cells are characterized by a flattened and enlarged morphology. Senescent cells become pro-inflammatory and contribute to the initiation and maintenance of sustained chronic sterile inflammation. Aging is associated with the accumulation of senescent cells in the cardiovascular system, and in general these cells are considered to be pathogenic because they mediate vascular remodeling. Recently, genetic and pharmacological approaches have enabled researchers to eliminate senescent cells both in vitro and in vivo. The term "senolysis" is now used to refer to the depletion of senescent cells, and evidence indicates that senolysis contributes to the reversal of age-related pathogenic phenotypes without the risk of tumorigenesis. The concept of senolysis has opened new avenues in research on aging, and senolysis may be a promising therapeutic approach for combating age-related disorders, including arterial diseases.
Pulmonary arterial hypertension (PAH) is characterized by remodeling and narrowing of the pulmona... more Pulmonary arterial hypertension (PAH) is characterized by remodeling and narrowing of the pulmonary arteries, which lead to elevation of right ventricular pressure, heart failure, and death. Proliferation of pulmonary artery smooth muscle cells (PASMCs) is thought to be central to the pathogenesis of PAH, although the underlying mechanisms are still being explored. The protein p53 is involved in cell cycle coordination, DNA repair, apoptosis, and cellular senescence, but its role in pulmonary hypertension (PH) is not fully known. We developed a mouse model of hypoxia-induced pulmonary hypertension (PH) and found significant reduction of p53 expression in the lungs. Our in vitro experiments with metabolomic analyses and the Seahorse XF extracellular flux analyzer indicated that suppression of p53 expression in PASMCs led to upregulation of glycolysis and downregulation of mitochondrial respiration, suggesting a proliferative phenotype resembling that of cancer cells. It was previously shown that systemic genetic depletion of p53 in a murine PH model led to more severe lung manifestations. Lack of information about the role of cell-specific p53 signaling promoted us to investigate it in our mouse PH model with the inducible Cre-loxP system. We generated a mouse model with SMC-specific gain or loss of p53 function by crossing Myh11-Cre/ERT2 mice with floxed Mdm4 mice or floxed Trp53 mice. After these animals were exposed to hypoxia for 4 weeks, we conducted hemodynamic and echocardiographic studies. Surprisingly, the severity of PH was similar in both groups of mice and there were no differences between the genotypes. Our findings in these mice indicate that activation or suppression of p53 signaling in SMCs has a minor role in the pathogenesis of PH and suggest that p53 signaling in other cells (endothelial cells, immune cells, or fibroblasts) may be involved in the progression of this condition.
Journal of Molecular and Cellular Cardiology, 2019
p53 is a guardian of the genome that protects against carcinogenesis. There is accumulating evide... more p53 is a guardian of the genome that protects against carcinogenesis. There is accumulating evidence that p53 is activated with aging. Such activation has been reported to contribute to various age-associated pathologies, but its role in vascular dysfunction is largely unknown. The aim of this study was to investigate whether activation of endothelial p53 has a pathological effect in relation to endothelial function. We established endothelial p53 loss-of-function and gain-of-function models by breeding endothelial-cell specific Cre mice with floxed Trp53 or floxed Mdm2/Mdm4 mice, respectively. Then we induced diabetes by injection of streptozotocin. In the diabetic state, endothelial p53 expression was markedly up-regulated and endothelium-dependent vasodilatation was significantly impaired. Impairment of vasodilatation was significantly ameliorated in endothelial p53 knockout (EC-p53 KO) mice, and deletion of endothelial p53 also significantly enhanced the induction of angiogenesis by ischemia. Conversely, activation of endothelial p53 by deleting Mdm2/Mdm4 reduced both endothelium-dependent vasodilatation and ischemia-induced angiogenesis. Introduction of p53 into human endothelial cells up-regulated the expression of phosphatase and tensin homolog (PTEN), thereby reducing phospho-eNOS levels. Consistent with these results, the beneficial impact of endothelial p53 deletion on endothelial function was attenuated in EC-p53 KO mice with an eNOS-deficient background. These results show that endothelial p53 negatively regulates endothelium-dependent vasodilatation and ischemia-induced angiogenesis, suggesting that inhibition of endothelial p53 could be a novel therapeutic target in patients with metabolic disorders.
In mammals, aging is associated with accumulation of senescent cells. Stresses such as telomere s... more In mammals, aging is associated with accumulation of senescent cells. Stresses such as telomere shortening and reactive oxygen species induce "cellular senescence", which is characterized by growth arrest and alteration of the gene expression profile. Chronological aging is associated with development of age-related diseases, including heart failure, diabetes, and atherosclerotic disease, and studies have shown that accumulation of senescent cells has a causative role in the pathology of these age-related disorders. Endothelial cell senescence has been reported to develop in heart failure and promotes pathologic changes in the failing heart. Senescent endothelial cells and vascular smooth muscle cells are found in atherosclerotic plaque, and studies indicate that these cells are involved in progression of plaque. Diabetes is also linked to accumulation of senescent vascular endothelial cells, while endothelial cell senescence per se induces systemic glucose intolerance by inhibiting skeletal muscle metabolism. A close connection between derangement of systemic metabolism and cellular senescence is also well recognized. Aging is a complex phenomenon, and there is no simple approach to understanding the whole process. However, there is accumulating evidence that cellular senescence has a central role in the development and progression of various undesirable aspects of aging. Suppression of cellular senescence or elimination of senescent cells reverses phenotypic changes of aging in several models, and proof-ofconcept has been established that inhibiting accumulation of senescent cells could become a next generation therapy for age-related disorders. It is clear that cellular senescence drives various pathological changes associated with aging. Accordingly, further investigation into the role of this biological process in age-related disorders and discovery of senolytic compounds are important fields for future exploration.
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...
Chronological aging is linked to cellular senescence, and there is accumulating evidence for a pa... more Chronological aging is linked to cellular senescence, and there is accumulating evidence for a pathological role of cellular senescence in age-related disorders such as obesity, diabetes, and heart failure. The protein p53 has a central role in cellular senescence, and p53 expression in cardiomyocytes, vascular endothelial cells, adipocytes, and immune cells leads to the development of heart failure and diabetes. It is widely accepted that formation of capillary networks is critical for morphogenesis of organs and maintenance of homeostasis. Capillary rarefaction and hypoxia promote pathological changes in the myocardium of the failing heart, causing systolic dysfunction. Capillary rarefaction and hypoxia also cause dysfunction of brown adipose tissue (BAT), leading to systemic metabolic disorders with promotion of diabetes. Vascular endothelial cell senescence develops in heart failure and diabetes and is responsible for progression of these age-related disorders. In a murine model of left ventricular pressure overload, increased expression of p53 in vascular endothelial cells and bone marrow cells promotes inflammatory cell infiltration into the heart, contributing to cardiac remodeling and systolic dysfunction. Metabolic stress up-regulates p53 expression in endothelial cells, while reducing the phosphorylation of endothelial nitric oxide synthase (eNOS) and glucose transporter (GLUT)1 expression in these cells. These changes lead to suppression of mitochondrial biogenesis and glucose uptake in the skeletal muscle and promote the development of systemic metabolic dysfunction. Suppression of vascular aging and vascular dysfunction is critically important for maintenance of organ homeostasis and is essential for prevention or treatment of heart failure, obesity, and diabetes.
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...
BACKGROUND/OBJECTIVES: Brain-derived neurotrophic factor (BDNF) and its receptor (tropomyosin-rel... more BACKGROUND/OBJECTIVES: Brain-derived neurotrophic factor (BDNF) and its receptor (tropomyosin-related kinase B: TrkB, also known as Ntrk2) have a key role in central regulation of the energy balance. BDNF and TrkB are also expressed in the peripheral tissues, including adipose tissue, but their peripheral role has been unclear. Here we report on the functional significance of the adipose tissue BDNF/TrkB axis in metabolic homeostasis. MATERIALS AND METHODS: To examine the role of the BDNF/TrkB axis in the central nervous system and in adipose tissue, we generated adipocyte-specific or neuron-specific BDNF/TrkB conditional knockout (CKO) mice. Then we compared the feeding behavior and metabolic profile between each type of CKO mouse and their littermates. RESULTS: Bdnf expression was significantly increased in the adipose tissue of mice receiving a high-calorie diet, whereas Ntrk2 expression was decreased. The Bdnf/Ntrk2 expression ratio of adipose tissue was higher in female mice than male mice. Fabp4-Cre mice are widely used to establish adipocyte-specific CKO mice. However, we found that Fabp4-Cre-induced deletion of Bdnf or Ntrk2 led to hyperphagia, obesity, and aggressiveness, presumably due to ectopic Fabp4-Cre mediated gene recombination in the brain. Next, we attempted to more specifically delete Bdnf or Ntrk2 in adipocytes using Adipoq-Cre mice. Expression of Ntrk2, but not Bdnf, in the adipose tissue was reduced by Adipoq-Cre mediated gene recombination, indicating that adipocytes only expressed TrkB. No phenotypic changes were detected when Adipoq-Cre TrkB CKO mice were fed a normal diet, whereas female CKO mice receiving a high-calorie diet showed a decrease in food intake and resistance to obesity. CONCLUSIONS: The adipose tissue BDNF/TrkB axis has a substantial influence on the feeding behavior and obesity in female mice.
Many human behaviors and physiological activities show circadian rhythms. Circadian rhythms gener... more Many human behaviors and physiological activities show circadian rhythms. Circadian rhythms generated by central and peripheral clocks maintain homeostasis, including the regulation of metabolic processes. Biological rhythmicity is important for metabolic health, but circadian rhythms are affected and impaired by nocturnal activities and irregular food intake in modern society. Disruption of sleep is an established risk factor for diabetes and is known to promote systemic metabolic dysfunction in both humans and rodents. Metabolic stress promotes circadian clock disorders and modulation of clock gene expression has a causal role in the development of metabolic dysfunction. Maintenance of a physiological circadian rhythm is crucial for metabolic health and is an important strategy for combating obesity.
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...
Obesity has dramatically increased throughout the world, and has become one of the chief healthca... more Obesity has dramatically increased throughout the world, and has become one of the chief healthcare problems in many societies. Evidence has emerged that adipose tissue dysfunction associated with obesity is critically involved in the development of cardiovascular and metabolic disorders. In this review, we delineate the link between adipose tissue abnormalities and systemic metabolic dysfunction in patients with cardio-metabolic diseases and discuss the underlying mechanisms.
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 ...
Prognosis of heart failure remains poor, and it is urgent to find new therapies for this critical... more Prognosis of heart failure remains poor, and it is urgent to find new therapies for this critical condition. Oxygen and metabolites are delivered through capillaries; therefore, they have critical roles in the maintenance of cardiac function. With aging or age-related disorders, capillary density is reduced in the heart, and the mechanisms involved in these processes were reported to suppress capillarization in this organ. Studies with rodents showed capillary rarefaction has causal roles for promoting pathologies in failing hearts. Drugs used as first-line therapies for heart failure were also shown to enhance the capillary network in the heart. Recently, the approach with senolysis is attracting enthusiasm in aging research. Genetic or pharmacological approaches concluded that the specific depletion of senescent cells, senolysis, led to reverse aging phenotype. Reagents mediating senolysis are described to be senolytics, and these compounds were shown to ameliorate cardiac dysfunction together with enhancement of capillarization in heart failure models. Studies indicate maintenance of the capillary network as critical for inhibition of pathologies in heart failure.
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...
Cell-proliferation potency is limited, as cells cannot proceed through the cell cycle continually... more Cell-proliferation potency is limited, as cells cannot proceed through the cell cycle continually. Instead, they eventually show an irreversible arrest of proliferation, commonly referred to as cellular senescence. Following the initial discovery of this phenomenon by Hayflick et al., studies have indicated that cells are also destined to undergo aging. In addition to the irreversible termination of proliferation, senescent cells are characterized by a flattened and enlarged morphology. Senescent cells become pro-inflammatory and contribute to the initiation and maintenance of sustained chronic sterile inflammation. Aging is associated with the accumulation of senescent cells in the cardiovascular system, and in general these cells are considered to be pathogenic because they mediate vascular remodeling. Recently, genetic and pharmacological approaches have enabled researchers to eliminate senescent cells both in vitro and in vivo. The term "senolysis" is now used to refer to the depletion of senescent cells, and evidence indicates that senolysis contributes to the reversal of age-related pathogenic phenotypes without the risk of tumorigenesis. The concept of senolysis has opened new avenues in research on aging, and senolysis may be a promising therapeutic approach for combating age-related disorders, including arterial diseases.
Pulmonary arterial hypertension (PAH) is characterized by remodeling and narrowing of the pulmona... more Pulmonary arterial hypertension (PAH) is characterized by remodeling and narrowing of the pulmonary arteries, which lead to elevation of right ventricular pressure, heart failure, and death. Proliferation of pulmonary artery smooth muscle cells (PASMCs) is thought to be central to the pathogenesis of PAH, although the underlying mechanisms are still being explored. The protein p53 is involved in cell cycle coordination, DNA repair, apoptosis, and cellular senescence, but its role in pulmonary hypertension (PH) is not fully known. We developed a mouse model of hypoxia-induced pulmonary hypertension (PH) and found significant reduction of p53 expression in the lungs. Our in vitro experiments with metabolomic analyses and the Seahorse XF extracellular flux analyzer indicated that suppression of p53 expression in PASMCs led to upregulation of glycolysis and downregulation of mitochondrial respiration, suggesting a proliferative phenotype resembling that of cancer cells. It was previously shown that systemic genetic depletion of p53 in a murine PH model led to more severe lung manifestations. Lack of information about the role of cell-specific p53 signaling promoted us to investigate it in our mouse PH model with the inducible Cre-loxP system. We generated a mouse model with SMC-specific gain or loss of p53 function by crossing Myh11-Cre/ERT2 mice with floxed Mdm4 mice or floxed Trp53 mice. After these animals were exposed to hypoxia for 4 weeks, we conducted hemodynamic and echocardiographic studies. Surprisingly, the severity of PH was similar in both groups of mice and there were no differences between the genotypes. Our findings in these mice indicate that activation or suppression of p53 signaling in SMCs has a minor role in the pathogenesis of PH and suggest that p53 signaling in other cells (endothelial cells, immune cells, or fibroblasts) may be involved in the progression of this condition.
Journal of Molecular and Cellular Cardiology, 2019
p53 is a guardian of the genome that protects against carcinogenesis. There is accumulating evide... more p53 is a guardian of the genome that protects against carcinogenesis. There is accumulating evidence that p53 is activated with aging. Such activation has been reported to contribute to various age-associated pathologies, but its role in vascular dysfunction is largely unknown. The aim of this study was to investigate whether activation of endothelial p53 has a pathological effect in relation to endothelial function. We established endothelial p53 loss-of-function and gain-of-function models by breeding endothelial-cell specific Cre mice with floxed Trp53 or floxed Mdm2/Mdm4 mice, respectively. Then we induced diabetes by injection of streptozotocin. In the diabetic state, endothelial p53 expression was markedly up-regulated and endothelium-dependent vasodilatation was significantly impaired. Impairment of vasodilatation was significantly ameliorated in endothelial p53 knockout (EC-p53 KO) mice, and deletion of endothelial p53 also significantly enhanced the induction of angiogenesis by ischemia. Conversely, activation of endothelial p53 by deleting Mdm2/Mdm4 reduced both endothelium-dependent vasodilatation and ischemia-induced angiogenesis. Introduction of p53 into human endothelial cells up-regulated the expression of phosphatase and tensin homolog (PTEN), thereby reducing phospho-eNOS levels. Consistent with these results, the beneficial impact of endothelial p53 deletion on endothelial function was attenuated in EC-p53 KO mice with an eNOS-deficient background. These results show that endothelial p53 negatively regulates endothelium-dependent vasodilatation and ischemia-induced angiogenesis, suggesting that inhibition of endothelial p53 could be a novel therapeutic target in patients with metabolic disorders.
In mammals, aging is associated with accumulation of senescent cells. Stresses such as telomere s... more In mammals, aging is associated with accumulation of senescent cells. Stresses such as telomere shortening and reactive oxygen species induce "cellular senescence", which is characterized by growth arrest and alteration of the gene expression profile. Chronological aging is associated with development of age-related diseases, including heart failure, diabetes, and atherosclerotic disease, and studies have shown that accumulation of senescent cells has a causative role in the pathology of these age-related disorders. Endothelial cell senescence has been reported to develop in heart failure and promotes pathologic changes in the failing heart. Senescent endothelial cells and vascular smooth muscle cells are found in atherosclerotic plaque, and studies indicate that these cells are involved in progression of plaque. Diabetes is also linked to accumulation of senescent vascular endothelial cells, while endothelial cell senescence per se induces systemic glucose intolerance by inhibiting skeletal muscle metabolism. A close connection between derangement of systemic metabolism and cellular senescence is also well recognized. Aging is a complex phenomenon, and there is no simple approach to understanding the whole process. However, there is accumulating evidence that cellular senescence has a central role in the development and progression of various undesirable aspects of aging. Suppression of cellular senescence or elimination of senescent cells reverses phenotypic changes of aging in several models, and proof-ofconcept has been established that inhibiting accumulation of senescent cells could become a next generation therapy for age-related disorders. It is clear that cellular senescence drives various pathological changes associated with aging. Accordingly, further investigation into the role of this biological process in age-related disorders and discovery of senolytic compounds are important fields for future exploration.
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...
Chronological aging is linked to cellular senescence, and there is accumulating evidence for a pa... more Chronological aging is linked to cellular senescence, and there is accumulating evidence for a pathological role of cellular senescence in age-related disorders such as obesity, diabetes, and heart failure. The protein p53 has a central role in cellular senescence, and p53 expression in cardiomyocytes, vascular endothelial cells, adipocytes, and immune cells leads to the development of heart failure and diabetes. It is widely accepted that formation of capillary networks is critical for morphogenesis of organs and maintenance of homeostasis. Capillary rarefaction and hypoxia promote pathological changes in the myocardium of the failing heart, causing systolic dysfunction. Capillary rarefaction and hypoxia also cause dysfunction of brown adipose tissue (BAT), leading to systemic metabolic disorders with promotion of diabetes. Vascular endothelial cell senescence develops in heart failure and diabetes and is responsible for progression of these age-related disorders. In a murine model of left ventricular pressure overload, increased expression of p53 in vascular endothelial cells and bone marrow cells promotes inflammatory cell infiltration into the heart, contributing to cardiac remodeling and systolic dysfunction. Metabolic stress up-regulates p53 expression in endothelial cells, while reducing the phosphorylation of endothelial nitric oxide synthase (eNOS) and glucose transporter (GLUT)1 expression in these cells. These changes lead to suppression of mitochondrial biogenesis and glucose uptake in the skeletal muscle and promote the development of systemic metabolic dysfunction. Suppression of vascular aging and vascular dysfunction is critically important for maintenance of organ homeostasis and is essential for prevention or treatment of heart failure, obesity, and diabetes.
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...
BACKGROUND/OBJECTIVES: Brain-derived neurotrophic factor (BDNF) and its receptor (tropomyosin-rel... more BACKGROUND/OBJECTIVES: Brain-derived neurotrophic factor (BDNF) and its receptor (tropomyosin-related kinase B: TrkB, also known as Ntrk2) have a key role in central regulation of the energy balance. BDNF and TrkB are also expressed in the peripheral tissues, including adipose tissue, but their peripheral role has been unclear. Here we report on the functional significance of the adipose tissue BDNF/TrkB axis in metabolic homeostasis. MATERIALS AND METHODS: To examine the role of the BDNF/TrkB axis in the central nervous system and in adipose tissue, we generated adipocyte-specific or neuron-specific BDNF/TrkB conditional knockout (CKO) mice. Then we compared the feeding behavior and metabolic profile between each type of CKO mouse and their littermates. RESULTS: Bdnf expression was significantly increased in the adipose tissue of mice receiving a high-calorie diet, whereas Ntrk2 expression was decreased. The Bdnf/Ntrk2 expression ratio of adipose tissue was higher in female mice than male mice. Fabp4-Cre mice are widely used to establish adipocyte-specific CKO mice. However, we found that Fabp4-Cre-induced deletion of Bdnf or Ntrk2 led to hyperphagia, obesity, and aggressiveness, presumably due to ectopic Fabp4-Cre mediated gene recombination in the brain. Next, we attempted to more specifically delete Bdnf or Ntrk2 in adipocytes using Adipoq-Cre mice. Expression of Ntrk2, but not Bdnf, in the adipose tissue was reduced by Adipoq-Cre mediated gene recombination, indicating that adipocytes only expressed TrkB. No phenotypic changes were detected when Adipoq-Cre TrkB CKO mice were fed a normal diet, whereas female CKO mice receiving a high-calorie diet showed a decrease in food intake and resistance to obesity. CONCLUSIONS: The adipose tissue BDNF/TrkB axis has a substantial influence on the feeding behavior and obesity in female mice.
Many human behaviors and physiological activities show circadian rhythms. Circadian rhythms gener... more Many human behaviors and physiological activities show circadian rhythms. Circadian rhythms generated by central and peripheral clocks maintain homeostasis, including the regulation of metabolic processes. Biological rhythmicity is important for metabolic health, but circadian rhythms are affected and impaired by nocturnal activities and irregular food intake in modern society. Disruption of sleep is an established risk factor for diabetes and is known to promote systemic metabolic dysfunction in both humans and rodents. Metabolic stress promotes circadian clock disorders and modulation of clock gene expression has a causal role in the development of metabolic dysfunction. Maintenance of a physiological circadian rhythm is crucial for metabolic health and is an important strategy for combating obesity.
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...
Obesity has dramatically increased throughout the world, and has become one of the chief healthca... more Obesity has dramatically increased throughout the world, and has become one of the chief healthcare problems in many societies. Evidence has emerged that adipose tissue dysfunction associated with obesity is critically involved in the development of cardiovascular and metabolic disorders. In this review, we delineate the link between adipose tissue abnormalities and systemic metabolic dysfunction in patients with cardio-metabolic diseases and discuss the underlying mechanisms.
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Papers by Ippei Shimizu