Pancreatic β-cells serve as a fuel sensor via secretion of insulin, which is controlled tightly by blood glucose concentration. The process of glucose-stimulated insulin secretion (GSIS) is explained ...as follows: Glucose, which has entered β-cells via glucose transporters (GLUT1 or 2), is phosphorylated by the rate-limiting enzyme glucokinase, which has a high Km for glucose. The product, glucose-6-phosphate, is further metabolized via glycolysis, tricarboxylic acid (TCA) cycle, and the electron transport chain to produce ATP, the central energy molecule. The increased ATP to ADP ratio in the cytosol prompts closure of ATP-sensitive K+ (KATP) channels. The resulting membrane depolarization leads to the activation of voltage-dependent Ca2+ channels, which triggers the exocytosis of insulin granules. Although this KATP channel-dependent pathway is considered to be a primary mechanism for GSIS, the involvement of KATP channel-independent actions in GSIS is also proposed. This is supported by the finding that glucose can augment the insulin secretion evoked by high K+ even under the condition where KATP channels are fully opened or closed pharmacologically.
Our previous studies have shown that phenylephrine-induced contraction of cutaneous arteries is primarily mediated via α1A-adrenoceptors, but not α1D-adrenoceptors that generally mediate vascular ...contraction, and that the larger part of the contraction is induced in a voltage-dependent Ca2+ channel (VDCC)-independent manner. Here, we investigated the mechanism underlying the smaller part of the α1A-adrenoceptor-mediated contraction, i.e., VDCC-dependent one, in cutaneous arteries. Isometric contraction was measured with wire myograph in endothelium-denuded tail and iliac arterial rings isolated from male Wistar rats. LOE908 (10 µM), a cation channel blocker, partially inhibited the contraction induced by phenylephrine in tail and iliac arteries. Nifedipine (10 µM) further suppressed the phenylephrine-induced contraction that remained in the presence of LOE908 (10 µM) in iliac arteries but barely in tail arteries, suggesting that phenylephrine-induced depolarization in tail arteries is due to the activation of LOE908-sensitive cation channels. In iliac arteries, the contraction induced by A-61603, a specific α1A-adrenoceptor agonist, was also partially inhibited by LOE908 (10 µM); however, nifedipine had little effect on the A-61603-induced contraction that remained in the presence of LOE908 (10 µM), suggesting that depolarization mediated via α1A-adrenoceptors is due to the activation of LOE908-sensitive cation channels even in iliac arteries. These results suggest that membrane depolarization mediated via α1Α-adrenoceptors is caused by cation influx through LOE908-sensitive cation channels. Less contribution of VDCC to phenylephrine-induced contraction in tail arteries compared to in iliac arteries is likely due to that α1Α-adrenoceptor-mediated activation of VDCC is caused only by depolarization via cation influx through LOE908-sensitive cation channels.
Previous our study found that improvement of skin blood flow associated with neuropathic pain using vasodilators is useful for alleviation of neuropathic pain. In this study, we aimed to elucidate ...the mechanism underlying enhanced vasorelaxation induced by vasodilators, which increase cAMP and cyclic guanosine monophosphate (cGMP), in chronic constriction injury model rat. We assessed vasorelaxation effect of vasodilators by measurement of isometric contraction in isolated plantar artery from chronic constriction injury of sciatic nerve model rats. Nifedipine, a voltage-dependent Ca2+ channel inhibitor, NS1619, Ca2+-activated K+ (BKCa) channel opener, and diazoxide, an ATP-sensitive potassium channel opener, -induced vasorelaxation in ipsilateral plantar artery was enhanced compared to the these in contralateral plantar artery. Sodium nitroprusside (SNP), a nitric oxide (NO) donor, and substance P, a NK1 receptor agonist, caused vasorelaxation in both ipsilateral and contralateral artery. The vasorelaxation induced by SNP and substance P in ipsilateral artery is enhanced compared to the these in contralateral artery. Isoprenaline, a β adrenoceptor agonist, and salbutamol, a β2 adrenoceptor agonist, caused strong vasorelaxation in ipsilateral artery but not in contralateral artery. Iberiotoxin, a BKCa channel inhibitor, prominently suppressed the enhanced vasorelaxation induced by SNP, substance P, isoprenaline and salbutamol. In summary, the enhanced contraction of arterial smooth muscle cell in skin artery is sensitive to hyperpolarization in chronic constriction injury model rat. Furthermore, β adrenoceptor agonist would be a good drug to improve the decreased skin blood flow because it has selective vasorelaxation to ipsilateral plantar artery.
Cognitive frailty (CF) is a clinical condition defined by the presence of both mild cognitive impairment (MCI) and physical frailty (PF). Elderly with CF are at greater risk of dementia than those ...with MCI or PF alone, but there are few known clinical or neuroimaging features to reliably distinguish CF from PF or MCI. We therefore conducted a population-based cross-sectional study of community elderly combining physical, cognitive, neuropsychiatric, and multisequence magnetic resonance imaging (MRI) evaluations. The MRI evaluation parameters included white matter (WM) lesion volumes, perivascular and deep subcortical WM lesion grades, lacunar infarct prevalence, microbleed number, and regional medial temporal lobe (MTL) volumes. Participants were divided into 4 groups according to the presence or absence of MCI and PF-(1) no MCI, PF (n = 27); (2) no PF, MCI (n = 119); (3) CF (MCI + PF) (n = 21), (4) normal controls (n = 716). Unique features of CF included shorter one-leg standing time; severe depressive symptoms; and MRI signs of significantly more WM lesions, lacunar infarcts, small-vessel disease lesions, microbleeds, and reduced MTL volumes. These unique deficits suggest that interventions for CF prevention and treatment should focus on motor skills, depressive symptoms, and vascular disease risk factor control.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
During liver injury, hepatic stellate cells (HSCs) are activated by various cytokines and transdifferentiated into myofibroblast-like activated HSCs, which produce collagen, a major source of liver ...fibrosis. Therefore, the suppression of HSC activation is regarded as a therapeutic target for liver fibrosis. Several epidemiological reports have revealed that caffeine intake decreases the risk of liver disease. In this study, therefore, we investigated the effect of caffeine on the activation of primary HSCs isolated from mice. Caffeine suppressed the activation of HSC in a concentration-dependent manner. BAPTA-AM, an intracellular Ca2+ chelator, had no effect on the caffeine-induced suppression of HSC activation. None of the isoform-selective inhibitors of phosphodiesterase1 to 5 affected changes in the morphology of HSC during activation, whereas CGS-15943, an adenosine receptor antagonist, inhibited them. Caffeine had no effect on intracellular cAMP level or on the phosphorylation of extracellular signal-regulated kinase (ERK)1/2. In contrast, caffeine significantly decreased the phosphorylation of Akt1. These results suggest that caffeine inhibits HSC activation by antagonizing adenosine receptors, leading to Akt1 signaling activation.
The role of type I diacylglycerol kinases (DGKs) in the regulation of insulin secretion was investigated in MIN6 β-cells. In intracellular Ca2+ concentration (Ca2+i) measurement experiments, 1 μM ...R59949, a type I DGK inhibitor, and 10 μM DiC8, a diacylglycerol (DAG) analog, amplified 22.2 mM glucose-induced Ca2+i oscillations in a protein kinase C (PKC)-dependent manner, whereas 10 μM R59949 and 100 μM DiC8 decreased Ca2+i independent of PKC. High concentrations of R59949 and DiC8 attenuated voltage-dependent Ca2+ channel currents. According to these results, 22.2 mM glucose-stimulated insulin secretion (GSIS) was potentiated by 1 μM R59949 but suppressed by 10 μM of the same. The DGKα inhibitor R59022 showed a similar dual effect. Conversely, DiC8 at 10 and 100 μM potentiated GSIS, although 100 μM DiC8 decreased Ca2+i. These results suggest that DAG accumulated through declined type I DGK activity shows a dual effect on insulin secretion depending on the degree of accumulation; a mild DAG accumulation induces a PKC-dependent stimulatory effect on insulin secretion, whereas an excessive DAG accumulation suppresses it in a PKC-independent manner, possibly via attenuation of VDCC activity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
An involvement of inducible nitric oxide (NO) synthase (NOS) in pancreatic β-cell degeneration during the process of type 1 diabetes has been well discussed. Recently, there is growing evidence for ...pivotal roles of constitutive NOS (cNOS) in β-cells; the presence of NOS1 and NOS3 in pancreatic β-cells and the effects of low-concentration NO, which is assumed to be derived from cNOS, on β-cell functions have been reported. However, the roles of cNOS-derived NO in β-cells are still under debate. One of the reasons seems to be that NO has multiple biological activities, which are dependent on its concentration. In β-cells, NO has been shown to exert positive and negative regulation of insulin secretion and anti- and pro-apoptotic activities, which is likely to be dependent on concentrations. In this review article, we will describe the current understanding of the roles of NO in pancreatic β-cells, especially focusing on cNOS-derived NO and its differential roles depending on concentrations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
High K+-induced contraction of arterial smooth muscle is thought to be mediated by membrane depolarization and subsequent activation of voltage-dependent Ca2+ channels (VDCCs). In line with this, ...this study found that contraction induced by 80 mM K+ was almost abolished by nifedipine (1 µM), a VDCC inhibitor, in isolated rat aorta, and was markedly suppressed in the iliac artery. However, nifedipine (1 µM) only partially suppressed high K+-induced contraction in the tail artery. The contractions remaining in the arteries were further reduced by non-selective cation channel (NSCC) inhibitors, including 2-aminoethoxydiphenyl borate (2-APB) (100 µM), SK&F96365 (10 µM), and 3,4-dihydro-6,7-dimethoxy-α-phenyl-N,N-bis2-(2,3,4-trimethoxyphenyl)ethyl-1-isoquinolineacetamide hydrochloride (LOE908) (10 µM). In particular, sustained tonic contraction was nearly abolished. Prazosin (0.3 µM), an α1-adrenoceptor antagonist, partially inhibited high K+-induced contraction in the tail and iliac arteries, but had no effect in the aorta. Consistently, tyramine potently induced contraction in the tail and iliac arteries, but not in the aorta. Furthermore, the inhibition by prazosin and NSCC inhibitors of the high K+-induced contraction in the presence of nifedipine was comparable. These results suggest that depending on the type of artery, high K+-induced contraction is mediated by Ca2+ influx not only through VDCCs but also through NSCCs, the activation of which is due to the activation of α1-adrenoceptors by the released noradrenaline from sympathetic nerve terminals resulting from high K+ stimulation.
The age of attention-deficit/hyperactivity disorder onset is usually during the first 12 years of life; however, there have been recent reports of late-onset attention-deficit/hyperactivity disorder. ...These reports have been limited to that of young adults, and details in older adults remain unknown. As such, we had previously presented the first case report of "very" late-onset attention-deficit/hyperactivity disorder, wherein the symptoms presented in senile age. In this observational study, we aimed to investigate the prevalence and clinical features of such attention-deficit/hyperactivity disorders in older adults visiting our dementia clinic.
Four hundred forty-six consecutive patients visiting our specialty outpatient clinic for dementia during the 2-year period from April 1, 2015 to March 31, 2017 were included in this study. First, the patients were examined for the presence or absence of dementia in our specialty outpatient clinic for dementia. Those not diagnosed with dementia were examined for the presence or absence of attention-deficit/hyperactivity disorder in our specialty outpatient clinic for developmental disorders. Finally, these patients who were diagnosed with attention-deficit/hyperactivity disorder were investigated in detail to clarify their clinical characteristics.
Of 446 patients (246 women and 200 men), 7 patients were finally diagnosed with attention-deficit/hyperactivity disorder. Although these 7 patients were initially suspected to have Alzheimer's disease (considering their age, 6 of these 7 patients were suspected to have early onset Alzheimer's disease), it was found that these symptoms were due to attention-deficit/hyperactivity disorder. These patients had four characteristics in common: (1) they were significantly younger than the complete study population; (2) they predominantly showed inattention-related symptoms; (3) they showed latent manifestation; and (4) they experienced a stressful life event before manifestation.
Our previous case report suggested that very late-onset attention-deficit/hyperactivity disorder patients could be incorrectly diagnosed with dementia. In this observational study, 1.6% of patients who were initially suspected of having dementia were actually diagnosed with attention-deficit/hyperactivity disorder. This study also showed that the "late-onset" described in our previous report would be better described as "late-manifestation." A clinician should consider late-manifestation of attention-deficit/hyperactivity disorder in the differential diagnosis when encountering dementia patients, especially early onset Alzheimer's disease.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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