Yasutaka Tanaka

Exendin-4, a glucagon-like peptide-1 receptor agonist, provides neuroprotection in mice transient focal cerebral ischemia

Glucagon-like peptide-1 (GLP-1) is an incretin hormone known to stimulate glucose-dependent insulin secretion. The GLP-1 receptor agonist, exendin-4, has similar properties to GLP-1 and is currently in clinical use for type 2 diabetes mellitus. As GLP-1 and exendin-4 confer cardioprotection after myocardial infarction, this study was designed to assess the neuroprotective effects of exendin-4 against cerebral ischemia–reperfusion injury. Mice received a transvenous injection of exendin-4, after a 60-minute focal cerebral ischemia. Exendin-4-treated vehicle and sham groups were evaluated for infarct volume, neurologic deficit score, various physiologic parameters, and immunohistochemical analyses at several time points after ischemia. Exendin-4 treatment significantly reduced infarct volume and improved functional deficit. It also significantly suppressed oxidative stress, inflammatory response, and cell death after reperfusion. Furthermore, intracellular cyclic AMP (cAMP) levels were slightly higher in the exendin-4 group than in the vehicle group. No serial changes were noted in insulin and glucose levels in both groups. This study suggested that exendin-4 provides neuroprotection against ischemic injury and that this action is probably mediated through increased intracellular cAMP levels. Exendin-4 is potentially useful in the treatment of acute ischemic stroke.

Single nucleotide polymorphisms in the gene encoding Krüppel-like factor 7 are associated with type 2 diabetes

Aims/hypothesisAlthough genetic susceptibility plays an important role in the pathogenesis of type 2 diabetes, most of the genes that influence susceptibility to type 2 diabetes have yet to be identified. Krüppel-like transcription factors are known to play important roles in development and cell differentiation, and have recently been implicated in the pathogenesis of type 2 diabetes. The present study aimed to examine the associations of single nucleotide polymorphisms (SNPs) in genes encoding members of the Krüppel-like-factor (KLF) family with type 2 diabetes in a large cohort of Japanese subjects.MethodsWe genotyped 33 SNP loci found in 12 KLF genes in subjects with type 2 diabetes and in subjects from the general population using the PCR-Invader assay. We also examined the effects of the overexpression of KLF7 on adipogenesis in 3T3-L1 cells.ResultsWe identified a significant association between an SNP in KLF7 and type 2 diabetes (A vs C: p=0.004 after Bonferroni’s correction, odds ratio=1.59, 95% CI 1.27–2.00). The expression of Klf7 decreased in response to the differentiation of 3T3-L1 adipocytes, and the overexpression of KLF7 resulted in significant inhibition of adipogenesis in 3T3-L1 cells.Conclusions/interpretationThese results indicate that the gene encoding KLF7 is a novel candidate for conferring genetic susceptibility to type 2 diabetes.

Prevalence of Abnormal Glucose Metabolism and Insulin Resistance Among Subtypes of Ischemic Stroke in Japanese Patients

Background and Purpose— The purpose was to assess the prevalence of disorders of glucose metabolism and insulin resistance in Japanese ischemic stroke patients with no history of diabetes by performing 75-gram oral glucose tolerance test (OGTT). Methods— We recruited 427 ischemic stroke patients (atherothrombotic infarction, n=220; lacunar infarction, n=125; cardioembolic infarction, n=82). OGTT was used to evaluate disorders of glucose metabolism in stroke patients without previously known diabetes (n=113). We investigated the relationships among the prevalence of abnormal glucose metabolism, ischemic stroke subtypes, and the prevalence of insulin resistance using homeostasis model assessment for insulin resistance and immunoreactive insulin at 120 minutes after glucose loading (IRI120). Results— OGTT identified the presence of disorders of glucose metabolism in 62.8% of ischemic stroke patients without previously known diabetes, including diabetes (24.8%) and impaired glucose tolerance (lone impaired glucose tolerance and impaired fasting glucose plus impaired glucose tolerance, 34.5%). The prevalence of newly diagnosed diabetes and impaired glucose tolerance was the highest in the atherothrombotic infarction group (68.9%). The highest values of homeostasis model assessment for insulin resistance and immunoreactive insulin at 120 minutes after glucose loading were found in atherothrombotic infarction patients with abnormal glucose tolerance. Conclusions— In this study, a significantly large percentage of Japanese patients with ischemic stroke and no history of diabetes were found to have disorders of glucose metabolism by OGTT. Impaired glucose tolerance and insulin resistance could play an important pathogenic role in the development of atherothrombotic infarction.

Cilostazol attenuates ischemic brain injury and enhances neurogenesis in the subventricular zone of adult mice after transient focal cerebral ischemia.

Evidence suggests that neurogenesis occurs in the adult mammalian brain, and that various stimuli, for example, ischemia/hypoxia, enhance the generation of neural progenitor cells in the subventricular zone (SVZ) and their migration into the olfactory bulb. In a mouse stroke model, focal ischemia results in activation of neural progenitor cells followed by their migration into the ischemic lesion. The present study assessed the in vivo effects of cilostazol, a type 3 phosphodiesterase inhibitor known to activate the cAMP-responsive element binding protein (CREB) signaling, on neurogenesis in the ipsilateral SVZ and peri-infarct area in a mouse model of transient middle cerebral artery occlusion. Mice were divided into sham operated (n=12), vehicle- (n=18) and cilostazol-treated (n=18) groups. Sections stained for 5-bromodeoxyuridine (BrdU) and several neuronal and a glial markers were analyzed at post-ischemia days 1, 3 and 7. Cilostazol reduced brain ischemic volume (P<0.05) and induced earlier recovery of neurologic deficit (P<0.05). Cilostazol significantly increased the density of BrdU-positive newly-formed cells in the SVZ compared with the vehicle group without ischemia. Increased density of doublecortin (DCX)-positive and BrdU/DCX-double positive neural progenitor cells was noted in the ipsilateral SVZ and peri-infarct area at 3 and 7 days after focal ischemia compared with the vehicle group (P<0.05). Cilostazol increased DCX-positive phosphorylated CREB (pCREB)-expressing neural progenitor cells, and increased brain derived neurotrophic factor (BDNF)-expressing astrocytes in the ipsilateral SVZ and peri-infarct area. The results indicated that cilostazol enhanced neural progenitor cell generation in both ipsilateral SVZ and peri-infarct area through CREB-mediated signaling pathway after focal ischemia.

Impact of diabetes and prediabetes on the short-term prognosis in patients with acute ischemic stroke.

OBJECTIVE We aimed to explore the association between abnormal glucose metabolism such as diabetes, prediabetes, and short-term prognosis in patients with acute ischemic stroke. METHODS Of 242 consecutive acute ischemic stroke patients, a 75-g oral glucose tolerance test was administered to 116 patients without previously diagnosed diabetes. One hundred forty patients were classified into diabetes, 52 patients were prediabetes (impaired glucose tolerance or impaired fasting glucose or both), and 50 patients were normal glucose tolerance (NGT). The association between each glycemic status and early neurological deterioration (END; increase in the NIH Stroke Scale (NIHSS) of ≥2 points during the first 14days after admission) or poor short-term outcome (30-day modified Ranking Scale [mRS] score 2-6) was evaluated. RESULTS In multivariable analysis, the risk of END was significantly higher in the diabetes group than in the NGT group (ORs=11.354; 95% CI, 1.492-86.415; p=0.019), even after adjustment for possible confounding factors (ORs=12.769; 95% CI, 1.361-119.763; p=0.026). Similar but insignificant associations were observed between prediabetes and NGT groups (ORs=6.369; 95% CI, 0.735-55.177; p=0.093). The risk of poor outcome (30-day mRS 2-6) was significantly higher in the diabetes group (ORs=3.667; 95% CI, 1.834-7.334; p<0.001) than in the NGT group, even after adjusting for confounding factors (ORs=3.340; 95% CI, 1.361-8.195; p=0.008). Similar but insignificant associations were observed between prediabetes and NGT groups (ORs=2.058; 95% CI, 0.916-4.623; p=0.08). CONCLUSION In our patient population, both diabetes and prediabetes were associated with a poor early prognosis after acute ischemic stroke.

Patent Foramen Ovale with Atrial Septal Aneurysm May Contribute to White Matter Lesions in Stroke Patients

Background: The purpose of the present study was to assess the contribution of embolic etiologies, patent foramen ovale (PFO) and atrial septal aneurysm (ASA), to cerebral white matter lesions (WMLs) in ischemic stroke patients. Methods: Patients with acute ischemic stroke who underwent transesophageal echocardiography were prospectively studied to investigate the relationships between the prevalence of PFO and ASA and the degree of WMLs. The patients were classified into four groups based on transesophageal echocardiography findings: (1) the PFO group (patients having PFO but not ASA); (2) the ASA group (patients having ASA but not PFO); (3) the PFO-ASA group (patients having both PFO and ASA), and (4) the non-septal abnormalities group (non-SA group, patients with neither PFO nor ASA). Based on MRI findings, the patients were also subdivided into grades 0, 1, 2, and 3 according to the Fazekas classification. Results: 115 patients (age, 69 ± 11 years; 41 females) were enrolled; 49 (43%) were in the PFO group, 4 (3%) were in the ASA group, 23 (20%) were in the PFO-ASA group, and 39 (34%) were in the non-SA group. The PFO-ASA group had significantly increased WMLs compared to the other three groups (p = 0.004). On multiple logistic regression analysis, the coexistence of PFO and ASA was significantly associated with the degree of WMLs (odds ratio: 2.40; 95% confidence interval: 1.11–5.17; p = 0.026) when the PFO-ASA and non-SA groups were compared. Conclusions: The coexistence of PFO with ASA could play an important pathogenic role in WML severity.

Amelioration of glucose tolerance by hepatic inhibition of nuclear factor κB in db/db mice

Aims/hypothesisRecent studies have identified the involvement of inhibitor IκB kinase (IKK) in the pathogenesis of insulin resistance. To investigate the mechanism involved, we examined the role of nuclear factor κB (NF-κB), the distal target of IKK, in hepatic glucose metabolism.MethodsTo inhibit NF-κB activity, db/db mice were infected with adenovirus expressing the IκBα super-repressor.ResultsThe IκBα super-repressor adenovirus infection caused a moderate reduction of NF-κB activity in liver. The treatment was associated with improved glucose tolerance, reduction in the serum insulin level, and increased hepatic triacylglycerol and glycogen contents, but had no effect on insulin-stimulated phosphorylation of Akt. On the other hand, quantification of mRNA in the liver revealed marked reduction of expression of gluconeogenic genes, such as those encoding phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase, concurrent with reduced expression of gene encoding peroxisome proliferator-activated receptor gamma coactivator-1α (PPARGC1A, also known as PGC-1α). Furthermore, the production of super-repressor IκBα suppressed the increase in blood glucose level after pyruvate injection.Conclusions/interpretationOur results indicate that moderate inhibition of NF-κB improved glucose tolerance through decreased gluconeogenesis associated with reduced PGC-1α gene expression in db/db mice, and suggest that inhibition of NF-κB activity in liver is a potentially suitable strategy for the normalisation of blood glucose concentration in type 2 diabetes.

Demographic, Clinical, and Radiologic Predictors of Neurologic Deterioration in Patients with Acute Ischemic Stroke

One-third of patients with acute ischemic stroke develop early neurologic worsening, which is associated with increased mortality and long-term functional disability. We investigated the predictive factors for neurologic deterioration in patients with acute ischemic stroke within 1 week of onset. We retrospectively investigated 643 patients who were admitted within 2 days of acute ischemic stroke between April 2007 and March 2010. Neurologic deterioration was defined as an increase of 4 points or more in the National Institutes of Health Stroke Scale (NIHSS) score within 1 week of admission. We retrieved data on demographic and clinical characteristics, medications, and stroke subtypes. Out of 537 patients, deterioration was noted in 64 patients (11.9%; deterioration group). Multivariate analysis identified history of myocardial infarction (P < .001), NIHSS score ≥8 at onset (P < .001), high leukocyte count (P = .035), low-density lipoprotein cholesterol ≥140 mg/dL (P = .002), and hemoglobin A1c ≥7% (P = .006) as significant factors associated with deterioration. Branch atheromatous disease was more frequent in the deterioration group, and >90% of patients with deterioration either were discharged to nursing home care or died. Multivariate analysis of magnetic resonance imaging findings identified internal carotid/middle cerebral artery occlusion (each P < .001), striate capsular infarction (P = .030), pontine infarction (P = .047), and lesion size of 15-30 mm (P = .011) as independent factors associated with deterioration. Stroke patients with a high low-density lipoprotein level, high hemoglobin A1c level on admission, a history of myocardial infarction, and high NIHSS score are at high risk for neurologic deterioration. Patients with multiple risk factors for deterioration can benefit most from intensive monitoring.

Polymorphism of the solute carrier family 12 (sodium/chloride transporters) member 3, SLC12A3, gene at exon 23 (+78G/A: Arg913Gln) is associated with elevation of urinary albumin excretion in Japanese patients with type 2 diabetes: a 10-year longitudinal study

Aims/hypothesisWe have shown previously that the SLC12A3 +78G/A polymorphism in exon 23 (Arg913Gln) was a new candidate for conferring susceptibility to diabetic nephropathy. The aim of this study was to confirm the effect of this polymorphism on the elevation of urinary albumin excretion in type 2 diabetic patients.MethodsWe retrospectively studied 264 Japanese patients with type 2 diabetes over a ten-year period. The subjects were classified into two groups: (1) persistent normoalbuminuria or microalbuminuria, or improvement from microalbuminuria to normoalbuminuria (group N); and (2) progression from normoalbuminuria to microalbuminuria or overt proteinuria, or progression from microalbuminuria to overt proteinuria (group P). They were assessed for association with the +78G/A polymorphism.ResultsThe frequency of the +78A allele was significantly higher in group N than in group P (10% vs 1%, p=0.021). By logistic regression analysis and discriminant analysis, the substituted allele was shown to be an independent factor correlating negatively to the elevation of albumin excretion (p=0.043 and 0.022, respectively).Conclusions/interpretationThe SLC12A3 +78A(+) genotype may have a protective effect against the development and/or progression of diabetic nephropathy in Japanese type 2 diabetic patients.

Visceral fat accumulation is associated with cerebral small vessel disease

Obesity is associated with the risk of coronary artery disease and stroke. Visceral fat plays a significant role in the atherogenic effects of obesity. Whether visceral fat accumulation, as measured by computed tomography (CT), is an independent risk factor for the presence of cerebral small vessel disease (SVD) was investigated.