Daisuke Sueta

Glycemic control with empagliflozin, a novel selective SGLT2 inhibitor, ameliorates cardiovascular injury and cognitive dysfunction in obese and type 2 diabetic mice

BackgroundThere has been uncertainty regarding the benefit of glycemic control with antidiabetic agents in prevention of diabetic macrovascular disease. Further development of novel antidiabetic agents is essential for overcoming the burden of diabetic macrovascular disease. The renal sodium glucose co-transporter 2 (SGLT2) inhibitor is a novel antihyperglycemic agent for treatment of type 2 diabetes. This work was performed to determine whether empagliflozin, a novel SGLT2 inhibitor, can ameliorate cardiovascular injury and cognitive decline in db/db mouse, a model of obesity and type 2 diabetes.Methods(1) Short-term experiment: The first experiment was performed to examine the effect of 7 days of empagliflozin treatment on urinary glucose excretion and urinary electrolyte excretion in db/db mice. (2) Long-term experiment: The second experiment was undertaken to examine the effect of 10 weeks of empagliflozin treatment on cardiovascular injury, vascular dysfunction, cognitive decline, and renal injury in db/db mice.Results(1) Short-term experiment: Empagliflozin administration significantly increased urinary glucose excretion, urine volume, and urinary sodium excretion in db/db mice on day 1, but did not increase these parameters from day 2. However, blood glucose levels in db/db mice were continuously decreased by empagliflozin throughout 7 days of the treatment. (2) Long-term experiment: Empagliflozin treatment caused sustained decrease in blood glucose in db/db mice throughout 10 weeks of the treatment and significantly slowed the progression of type 2 diabetes. Empagliflozin significantly ameliorated cardiac interstitial fibrosis, pericoronary arterial fibrosis, coronary arterial thickening, cardiac macrophage infiltration, and the impairment of vascular dilating function in db/db mice, and these beneficial effects of empagliflozin were associated with attenuation of oxidative stress in cardiovascular tissue of db/db mice. Furthermore, empagliflozin significantly prevented the impairment of cognitive function in db/db mice, which was associated with the attenuation of cerebral oxidative stress and the increase in cerebral brain-derived neurotrophic factor. Empagliflozin ameliorated albuminuria, and glomerular injury in db/db mice.ConclusionsGlycemic control with empagliflozin significantly ameliorated cardiovascular injury and remodeling, vascular dysfunction, and cognitive decline in obese and type 2 diabetic mice. Thus, empagliflozin seems to be potentially a promising therapeutic agent for diabetic macrovascular disease and cognitive decline.

Perindopril, a centrally active angiotensin-converting enzyme inhibitor, prevents cognitive impairment in mouse models of Alzheimer's disease

The purpose of this work was to test whether brain‐penetrating angiotensin‐converting enzyme (ACE) inhibitors (e.g., perindopril), as opposed to non‐brain‐penetrating ACE inhibitors (e.g., enalapril and imidapril), may reduce the cognitive decline and brain injury in Alzheimers disease (AD). We first compared the effect of perindopril, enalapril, and imidapril on cognitive impairment and brain injury in a mouse model of AD induced by intracerebroventricular (i.c.v.) injection of amyloid‐β (Aβ)1–40. Perindopril, with significant inhibition of hippocampal ACE, significantly prevented cognitive impairment in this AD mouse model. This beneficial effect was attributed to the suppression of microglia/astrocyte activation and the attenuation of oxidative stress caused by iNOS induction and extracellular superoxide dismutase down‐regulation. In contrast, neither enalapril nor imidapril prevented cognitive impairment and brain injury in this AD mouse. We next examined the protective effects of perindopril on cognitive impairment in PS2APP‐transgenic mice overexpressing Aβ in the brain. Perindopril, without affecting brain Aβ deposition, significantly suppressed the increase in hippocampal ACE activity and improved cognition in PS2APP‐transgenic mice, being associated with the suppression of hippocampal astrocyte activation and attenuation of superoxide. Our data demonstrated that the brain‐penetrating ACE inhibitor perindopril, as compared to non‐brain‐penetrating ACE inhibitors, protected against cognitive impairment and brain injury in experimental AD models.—Dong, Y. ‐F., Kataoka, K., Tokutomi, Y., Nako, H., Nakamura, T., Toyama, K., Sueta, D., Koibuchi, N., Yamamoto, E., Ogawa, H., Kim‐Mitsuyama, S. Perindopril, a centrally active angiotensin‐converting enzyme inhibitor, prevents cognitive impairment in mouse models of Alzheimers disease. FASEB J. 25, 2911–2920 (2011). www.fasebj.org

Attenuation of Brain Damage and Cognitive Impairment by Direct Renin Inhibition in Mice With Chronic Cerebral Hypoperfusion

The role of the renin-angiotensin system in cognitive impairment is unclear. This work was undertaken to test our hypothesis that renin-angiotensin system may contribute to cognitive decline and brain damage caused by chronic cerebral ischemia. C57BL/6J mice were subjected to bilateral common carotid artery stenosis with microcoil to prepare mice with chronic cerebral hypoperfusion, a model of subcortical vascular dementia. The effects of aliskiren, a direct renin inhibitor, or Tempol, a superoxide scavenger, on brain damage and working memory in these mice were examined. Chronic cerebral hypoperfusion significantly increased brain renin activity and angiotensinogen expression in C57BL/6J mice, which was attributed to the increased renin in activated astrocytes and microvessels and the increased angiotensinogen in activated astrocytes in white matter. Aliskiren pretreatment significantly inhibited brain renin activity and ameliorated brain p67phox-related NADPH oxidase activity, oxidative stress, glial activation, white matter lesion, and spatial working memory deficits in C57BL/6J mice with bilateral common carotid artery stenosis. To elucidate the role of oxidative stress in brain protective effects of aliskiren, we also examined the effect of Tempol in the same mice with bilateral common carotid artery stenosis. Tempol pretreatment mimicked the brain protective effects of aliskiren in this mouse model. Posttreatment of mice with aliskiren or Tempol after bilateral common carotid artery stenosis also prevented cognitive decline. In conclusion, chronic cerebral hypoperfusion induced the activation of the brain renin-angiotensin system. Aliskiren ameliorated brain damage and working memory deficits in the model of chronic cerebral ischemia through the attenuation of oxidative stress. Thus, direct renin inhibition seems to be a promising therapeutic strategy for subcortical vascular dementia.

Apoptosis Signal–Regulating Kinase 1 Is a Novel Target Molecule for Cognitive Impairment Induced by Chronic Cerebral Hypoperfusion

Objective— There are currently no specific strategies for the treatment or prevention of vascular dementia. White matter lesions, a common pathology in cerebral small vessel disease, are a major cause of vascular dementia. We investigated whether apoptosis signal–regulating kinase 1 (ASK1) might be a key molecule in cerebral hypoperfusion, associated with blood–brain barrier breakdown and white matter lesions. Approach and Results— A mouse model of cognitive impairment was developed by inducing chronic cerebral hypoperfusion in white matter including the corpus callosum via bilateral common carotid artery stenosis (BCAS) surgery. BCAS-induced white matter lesions caused cognitive decline in C57BL/6J (wild-type) mice but not in ASK1-deficient (ASK1−/−) mice. Phosphorylated ASK1 increased in wild-type mouse brains, and phosphorylated p38 and tumor necrosis factor-&agr; expression increased in corpus callosum cerebral endothelial cells after BCAS in wild-type mice but not in ASK1−/− mice. BCAS decreased claudin-5 expression and disrupted blood–brain barrier in the corpus callosum of wild-type but not ASK1−/− mice. Cerebral nitrotyrosine was increased in wild-type and ASK1−/− BCAS mice. Cerebral phosphorylated ASK1 did not increase in wild-type mice treated with NADPH-oxidase inhibitor. A p38 inhibitor and NADPH-oxidase inhibitor mimicked the protective effect of ASK1 deficiency against cognitive impairment. Specific ASK1 inhibitor prevented cognitive decline in BCAS mice. In vitro oxygen-glucose deprivation and tumor necrosis factor-&agr; stimulation caused the disruption of endothelial tight junctions from wild-type mice but not ASK1−/− mice. Conclusions— Oxidative stress-ASK1-p38 cascade plays a role in the pathogenesis of cognitive impairment, through blood–brain barrier breakdown via the disruption of endothelial tight junctions. ASK1 might be a promising therapeutic target for chronic cerebral hypoperfusion–induced cognitive impairment.

Long-Term Renal Denervation Normalizes Disrupted Blood Pressure Circadian Rhythm and Ameliorates Cardiovascular Injury in a Rat Model of Metabolic Syndrome

Background Although renal denervation significantly reduces blood pressure in patients with resistant hypertension, the role of the renal nerve in hypertension with metabolic syndrome is unknown. We investigated the impact of long‐term renal denervation on SHR/NDmcr‐cp(+/+) (SHRcp) rats, a useful rat model of metabolic syndrome, to determine the role of the renal nerve in hypertension with metabolic syndrome. Methods and Results SHRcp rats were divided into (1) a renal denervation (RD) group and (2) a sham operation group (control) to examine the effects of long‐term RD on blood pressure circadian rhythm, renal sodium retention‐related molecules, the renin‐angiotensin‐aldosterone system, metabolic disorders, and organ injury. RD in SHRcp rats not only significantly reduced blood pressure but also normalized blood pressure circadian rhythm from the nondipper to the dipper type, and this improvement was associated with an increase in urinary sodium excretion and the suppression of renal Na+‐Cl− cotransporter upregulation. RD significantly reduced plasma renin activity. RD significantly prevented cardiovascular remodeling and impairment of vascular endothelial function and attenuated cardiovascular oxidative stress. However, RD failed to ameliorate obesity, metabolic disorders, and renal injury and failed to reduce systemic sympathetic activity in SHRcp rats. Conclusions By including the upregulation of the Na+‐Cl− cotransporter, the renal sympathetic nerve is involved in the disruption of blood pressure circadian rhythm as well as hypertension in metabolic syndrome. Thus, RD seems to be a useful therapeutic strategy for hypertension with metabolic syndrome.

Novel Mechanism for Disrupted Circadian Blood Pressure Rhythm in a Rat Model of Metabolic Syndrome—The Critical Role of Angiotensin II

Background This study was performed to determine the characteristics and mechanism of hypertension in SHR/NDmcr‐cp(+/+) rats (SHRcp), a new model of metabolic syndrome, with a focus on the autonomic nervous system, aldosterone, and angiotensin II. Methods and Results We measured arterial blood pressure (BP) in SHRcp by radiotelemetry combined with spectral analysis using a fast Fourier transformation algorithm and examined the effect of azilsartan, an AT1 receptor blocker. Compared with control Wistar‐Kyoto rats (WKY) and SHR, SHRcp exhibited a nondipper‐type hypertension and displayed increased urinary norepinephrine excretion and increased urinary and plasma aldosterone levels. Compared with WKY and SHR, SHRcp were characterized by an increase in the low‐frequency power (LF) of systolic BP and a decrease in spontaneous baroreflex gain (sBRG), indicating autonomic dysfunction. Thus, SHRcp are regarded as a useful model of human hypertension with metabolic syndrome. Oral administration of azilsartan once daily persistently lowered BP during the light period (inactive phase) and the dark period (active phase) in SHRcp more than in WKY and SHR. Thus, angiotensin II seems to be involved in the mechanism of disrupted diurnal BP rhythm in SHRcp. Azilsartan significantly reduced urinary norepinephrine and aldosterone excretion and significantly increased urinary sodium excretion in SHRcp. Furthermore, azilsartan significantly reduced LF of systolic BP and significantly increased sBRG in SHRcp. Conclusions These results strongly suggest that impairment of autonomic function and increased aldosterone in SHRcp mediate the effect of angiotensin II on circadian blood pressure rhythms.

Renal Denervation Prevents Stroke and Brain Injury via Attenuation of Oxidative Stress in Hypertensive Rats

Background Although renal denervation (RD) is shown to reduce blood pressure significantly in patients with resistant hypertension, the benefit of RD in prevention of stroke is unknown. We hypothesized that RD can prevent the incidence of stroke and brain injury in hypertensive rats beyond blood pressure lowering. Methods and Results High‐salt‐loaded, stroke‐prone, spontaneously hypertensive rats (SHRSP) were divided into 4 groups: (1) control; (2) sham operation; (3) bilateral RD; and (4) hydralazine administration to examine the effect of RD on stroke and brain injury of SHRSP. RD significantly reduced the onset of neurological deficit and death in SHRSP, and this protection against stroke by RD was associated with the increase in cerebral blood flow (CBF), the suppression of blood–brain barrier disruption, the limitation of white matter (WM) lesions, and the attenuation of macrophage infiltration and activated microglia. Furthermore, RD significantly attenuated brain oxidative stress, and NADPH oxidase subunits, P67 and Rac1 in SHRSP. On the other hand, hydralazine, with similar blood pressure lowering to RD, did not significantly suppress the onset of stroke and brain injury in SHRSP. Furthermore, RD prevented cardiac remodeling and vascular endothelial impairment in SHRSP. Conclusions Our present work provided the first experimental evidence that RD can prevent hypertensive stroke and brain injury, beyond blood pressure lowering, thereby highlighting RD as a promising therapeutic strategy for stroke as well as hypertension.

Pretreatment with rosuvastatin protects against focal cerebral ischemia/reperfusion injury in rats through attenuation of oxidative stress and inflammation.

This study aimed to examine the potential protective effect of rosuvastatin against cerebral ischemia/reperfusion injury and its mechanisms. Forty-eight male SD rats underwent 90 min of transient middle cerebral artery occlusion (tMCAO), followed by reperfusion. Rats were orally given (1) rosuvastatin 1mg/kg, (2) rosuvastatin 10mg/kg or (3) water (vehicle) once a day from 7 days before to 1 day after induction of tMCAO. Neurological score, infarct volume, and oxidative stress-related molecules (assessed by immunohistochemistry, dihydroethidium staining, or western blotting) were estimated at 24h after reperfusion. Rosuvastatin prevented the impairment of neurological function and decreased the infarct volume, compared with the vehicle group. The increases in activated microglia, macrophage, and superoxide levels usually caused by ischemia/reperfusion were significantly ameliorated by rosuvastatin. Rosuvastatin also inhibited the upregulation of gp91(phox) and p22phox, phosphorylation of nuclear factor-kappa B, and induction of cyclooxygenase 2 and inducible nitric oxide synthase, compared with vehicle. The results suggest that pretreatment with rosuvastatin may be a promising therapeutic strategy for cerebral ischemia/reperfusion injury, through attenuation of oxidative stress and inflammation.

Beneficial effects of combination of valsartan and amlodipine on salt-induced brain injury in hypertensive rats

The optimum antihypertensive treatment for prevention of hypertensive stroke has yet to be elucidated. This study was undertaken to examine the benefit of a combination of valsartan, an angiotensin II type 1 (AT1) receptor blocker, and amlodipine, a calcium channel blocker, in prevention of high-salt-induced brain injury in hypertensive rats. High-salt-loaded stroke-prone spontaneously hypertensive rats (SHRSPs) were given 1) vehicle, 2) valsartan (2 mg/kg/day), 3) amlodipine (2 mg/kg/day), or 4) a combination of valsartan and amlodipine for 4 weeks. The effects on brain injury were compared between all groups. High-salt loading in SHRSPs caused the reduction of cerebral blood flow (CBF), cerebral hypoxia, white matter lesions, glial activation, AT1 receptor up-regulation, endothelial nitric-oxide synthase (eNOS) uncoupling, inducible nitric-oxide synthase induction, and nitroxidative stress. Valsartan, independently of blood pressure, enhanced the protective effects of amlodipine against brain injury, white matter lesions, and glial activation in salt-loaded SHRSPs. These beneficial effects of valsartan added to amlodipine were associated with an additive improvement in CBF and brain hypoxia because of an additive improvement in cerebral arteriolar remodeling and vascular endothelial dysfunction. Furthermore, valsartan added to amlodipine enhanced the attenuation of cerebral nitroxidative stress through an additive suppression of eNOS uncoupling. Valsartan, independently of blood pressure, augmented the protective effects of amlodipine against brain injury in salt-loaded hypertensive rats through an improvement in brain circulation attributed to nitroxidative stress. Our results suggest that the combination of valsartan and amlodipine may be a promising strategy for the prevention of salt-related brain injury in hypertensive patients.

A novel quantitative assessment of whole blood thrombogenicity in patients treated with a non-vitamin K oral anticoagulant

Non-vitamin K oral anticoagulants(NOAC) negate complex patient management issues, such as frequent blood sampling, diet restriction, and drug interactions, that had to be dealt with during the warfarinonly era. However, there is no definite tool tomonitor the anticoagulant effects of NOACs, although some patients suffer from bleeding complications related to exceedingly high blood concentrations of NOACs. [1, 2] Routine tests, such as prothrombin time-international normalized ratio (PT-INR) and activated partial thromboplastin time (APTT), can be problematic formonitoring the anticoagulant effects of all NOACs because each individual NOAC has a different characteristic chemical structure and different pharmacokinetic profile (e.g., plasma half-life and tissue penetration rate) [3]. Recently, the Total Thrombus-formation Analysis System (T-TASTM) [4,5], a microchip-based flow chamber system capable of evaluating whole blood thrombogenicity, was developed as an easy-to-use system for quantitative analysis of thrombus formation (Fig. 1A,B). In the present study, we sought to examine whether the T-TASTM was useful for the quantitative analysis of thrombogenicity in patients treated with the NOAC edoxaban (Fig. 1C, D). We recruited 20 consecutive patients (male: n = 8 [40%] and female: n=12 [60%], average age: 75.2±8.7 years)whowere scheduled