CNS injury, γ1 laminin, and its KDI peptide

Nisäkkäillä keskushermoston uudistuminen on rajallista. Keskushermostovamman jälkeen aktivoituu monien paranemista edistävien tekijöiden lisäksi myös estäviä tekijöitä. Monella molekyylillä, kuten laminiinilla, on keskushermoston paranemista tehostava vaikutus. Laminiinit ovat myös kehon tyvikalvojen oleellisia rakennuskomponentteja. Keskushermoston laminiinit ovat tärkeitä sikiökehityksen aikana, esimerkiksi hermosäikeiden ohjauksessa. Myöhemmin ne osallistuvat veriaivoesteen ylläpitoon sekä vammojen jälkeiseen kudosreaktioon. Väitöskirjatutkimuksessani olen selvittänyt lamiiniinien, erityisesti γ1 laminiinin ja sen KDI peptidin, ekspressiota keskushermoston vammatilanteissa. Kokeellisessa soluviljelmäasetelmassa, joka simuloi vammautunutta keskushermostoympäristöä, osoitimme että KDI peptidi voimistaa sekä hermosolujen selviytymistä että hermosäikeiden kasvua. Kainihappo on glutamaattianalogi, ja glutamaattitoksisuudella uskotaan olevan tärkeä merkitys keskushermoston eri vamma- ja sairaustilanteissa tapahtuvassa hermosolukuolemassa. Toisessa väitöskirjani osatyössä osoitimme eläinmallissa KDI peptidin suojaavan rotan aivojen hippokampuksen hermosoluja kainihapon aiheuttamalta solutuholta. Elektrofysiologisilla mittauksilla osoitimme kolmannessa osatyössäni, että KDI peptidi estää glutamaattireseptorivirtoja ja suojaa siten glutamaattitoksisuudelta. Aivoveritulpan aiheuttama aivovaurio on yleinen syy aivohalvaukseen. Viimeisessä osatyössäni tutkimme eläinmallissa laminiinien ekspressiota iskemian vaurioittamassa aivokudoksessa. Laminiiniekspression todettiin voimistuvan vaurion jälkeen sekä tyvikalvo- että soluväliainerakenteissa. Vaurion ympärillä havaittiin astrosyyttejä, jotka jo melko aikaisessa vaiheessa vamman jälkeen ekspressoivat γ1 laminiinia ja KDI peptidiä. Tästä voidaan päätellä laminiinien osallistuvan aivoiskeemisen vaurion patofysiologiaan. Yleisesti väitöskirjatyöni kartoitti laminiinien ekspressiota sekä terveessä että vammautuneessa keskushermostossa. Väitöskirjatyöni tukee hypoteesia, jonka mukaan KDI peptidi suojaa keskushermostoa vaurioilta.The regeneration capacity of the adult mammalian central nervous system (CNS) is limited. Following an insult to the CNS, many environmental factors inhibiting or stimulating neuronal regrowth are activated. Several molecules including laminin have stimulating effects on CNS regeneration. Laminins are essential molecular constituents of all basement membranes of the body. In the CNS, laminins are involved in developmental events, such as neuronal migration and axon guidance, while in the adult CNS they participate in the formation and maintenance of the blood-brain-barrier (BBB) and are involved in trauma reactions of the CNS. Laminin-1 is a large glycoprotein and is composed from three disulfide-bonded subunits, α1, β1, and the γ1 chain. Many neurons express γ1 laminin in the mammalian adult brain; it is critical for hippocampal neuronal survival and is expressed by glial cells after CNS injury. The KDI peptide is derived from γ1 laminin as a neurotrophic peptide. In this thesis study, we analyzed the role of γ1 laminin and its KDI peptide in different settings of CNS injury. An experimental cell culture model mimicking a damaged CNS environment showed that the KDI peptide has a stimulating effect on neuronal survival and neurite outgrowth. We analyzed neurons from human embryonic spinal cord, retina, and neocortex, leading to findings that both neuronal survival and neurite outgrowth were stimulated by the soluble KDI peptide in all of these tissues. A stereotaxic injection of kainic acid into rat hippocampus was done for testing the possible protective effect of the KDI peptide. A preceding injection of the KDI peptide protected both hippocampal and neocortical areas of excitotoxic brain damage caused by kainic acid. Kainic acid alone caused serious tissue damage to the hippocampal and neocortical injection sites. The KDI peptide showed inhibition of glutamate excitotoxicity by inhibiting kainate, AMPA, and NMDA subclasses of glutamate receptors in patch clamp recordings. Neurons were cultured from human embryonic neocortex and from HEK 293 cells expressing recombinant glutamate subunits. These studies indicate that the KDI peptide of γ1 laminin enhances neuronal survival and protects against glutamate excitotoxicity at least partially through inhibition of various glutamate receptors. Following middle cerebral artery occlusion leading to focal brain ischemia in rats, various laminins were mapped both spatially and temporally. Laminin-1 was increased in basement membranes and scar-forming extracellular matrix; γ1 laminin was in-duced earlier than other laminins and expressed by reactive astrocytes. Similarly, the KDI peptide of γ1 laminin was expressed by reactive astrocytes surrounding the ischemic region but detected along major neuronal pathways as well. The different patterns of laminin expression suggest involvement of different laminins in different functions in the pathophysiology of experimental brain ischemia. In general, these studies present novel data on the expression of laminins in the healthy and damaged brain, demonstrate protective effects of the KDI tripeptide of γ1 laminin in cell cultures and in vivo in the brain, and give clues as to the mechanisms of KDI peptide neuroprotection

Spinal Epidural Hematoma as a Complication of Intravenous Thrombolysis in an Acute Ischemic Stroke Patient

An 80-year-old white male suffered a stroke, fell to the floor, and suffered acute right hemiparesis and facial palsy. After an intravenous alteplase infusion 2.5 h later, the patient first complained of numbness in his right arm, then neck pain, followed by left leg numbness and slowly progressing paraparesis. MRI of the spine demonstrated an acute spinal dorsal epidural hematoma extending from the C6 to the T6 level; 12 h later, he underwent hematoma evacuation and laminectomy. Three months after surgery, the patient was paraplegic with moderate sensory loss below mamillary level. Acute ischemic stroke is often associated with a sudden fall, which, after thrombolysis, may result in unusual hemorrhagic complications

Clinical and MRI Features of Cerebral Small-Vessel Disease in Type 1 Diabetes

OBJECTIVETo assess the prevalence of cerebral small-vessel disease (SVD) in subjects with type 1 diabetes compared with healthy control subjects and to characterize the diabetes-related factors associated with SVD.RESEARCH DESIGN AND METHODSThis substudy was cross-sectional in design and included 191 participants with type 1 diabetes and median age 40.0 years (interquartile range 33.0-45.1) and 30 healthy age- and sex-matched control subjects. All participants underwent clinical investigation and brain MRIs, assessed for cerebral SVD.RESULTSCerebral SVD was more common in participants with type 1 diabetes than in healthy control subjects: any marker 35% vs. 10% (P = 0.005), cerebral microbleeds (CMBs) 24% vs. 3.3% (P = 0.008), white matter hyperintensities 17% vs. 6.7% (P = 0.182), and lacunes 2.1% vs. 0% (P = 1.000). Presence of CMBs was independently associated with systolic blood pressure (odds ratio 1.03 [95% CI 1.00-1.05], P = 0.035).CONCLUSIONSCerebral SVD, CMBs in particular, is more common in young people with type 1 diabetes compared with healthy control subjects.Peer reviewe

Carotid intima-media thickness and arterial stiffness in relation to cerebral small vessel disease in neurologically asymptomatic individuals with type 1 diabetes

Aims To determine if arterial functional and structural changes are associated with underlying cerebral small vessel disease in neurologically asymptomatic individuals with type 1 diabetes. Methods We enrolled 186 individuals (47.8% men; median age 40.0, IQR 33.0-45.0 years) with type 1 diabetes (median diabetes duration of 21.6, IQR 18.2-30.3 years), and 30 age- and sex-matched healthy controls, as part of the Finnish Diabetic Nephropathy (FinnDiane) Study. All individuals underwent a biochemical work-up, brain magnetic resonance imaging (MRI), ultrasound of the common carotid arteries and arterial tonometry. Arterial structural and functional parameters were assessed by carotid intima-media thickness (CIMT), pulse wave velocity and augmentation index. Results Cerebral microbleeds (CMBs) were present in 23.7% and white matter hyperintensities (WMHs) in 16.7% of individuals with type 1 diabetes. Those with type 1 diabetes and CMBs had higher median (IQR) CIMT 583 (525 - 663) mu m than those without 556 (502 - 607) mu m, p = 0.016). Higher CIMT was associated with the presence of CMBs (p = 0.046) independent of age, eGFR, ApoB, systolic blood pressure, albuminuria, history of retinal photocoagulation and HbA(1c). Arterial stiffness and CIMT were increased in individuals with type 1 diabetes and WMHs compared to those without; however, these results were not independent of cardiovascular risk factors. Conclusions Structural, but not functional, arterial changes are associated with underlying CMBs in asymptomatic individuals with type 1 diabetes.Peer reviewe

Cerebral small-vessel disease is associated with the severity of diabetic retinopathy in type 1 diabetes

Introduction Cerebral small-vessel disease is common in neurologically asymptomatic individuals with type 1 diabetes. The retinal vasculature is thought to mirror the brain's vasculature, but data on this association are limited in type 1 diabetes. Our aim was to study associations between diabetic retinopathy severity and cerebral small-vessel disease in type 1 diabetes. Research design and methods For this cross-sectional study, we enrolled 189 participants with type 1 diabetes (median age 40 (33-45) years; 53% female; diabetes duration 21.6 (18.2-30.7) years) and 29 healthy age-matched and sex-matched controls as part of the Finnish Diabetic Nephropathy Study. Participants underwent a clinical investigation, brain MRI, and fundus imaging. Signs of cerebral small-vessel disease in brain MRIs were analyzed in relation to diabetic retinopathy severity (Early Treatment Diabetic Retinopathy Study (ETDRS) score). Results In type 1 diabetes, participants with cerebral small-vessel disease had higher ETDRS scores (35 (20-61) vs 20 (20-35), p=0.022) and a higher prevalence of proliferative diabetic retinopathy than those without cerebral small-vessel disease (25% vs 9%, p=0.002). In adjusted analysis, proliferative diabetic retinopathy was associated with cerebral small-vessel disease (OR 2.57 (95% CI 1.04 to 6.35)). Median ETDRS score (35 (20-65) vs 20 (20-35), p=0.024) and proliferative diabetic retinopathy prevalence were higher (29% vs 13%, p=0.002) in participants with versus without cerebral microbleeds. ETDRS scores increased by number of cerebral microbleeds (p=0.001), both ETDRS score (OR 1.05 (95% CI 1.02 to 1.09)) and proliferative diabetic retinopathy (8.52 (95% CI 1.91 to 37.94)) were associated with >2 cerebral microbleeds in separate multivariable analysis. We observed no association with white matter hyperintensities or lacunar infarcts. Conclusions Presence of cerebral small-vessel disease on brain MRI, particularly cerebral microbleeds, is associated with the severity of diabetic retinopathy.Peer reviewe

Comparison of Manual Cross-Sectional Measurements and Automatic Volumetry of the Corpus Callosum, and Their Clinical Impact: A Study on Type 1 Diabetes and Healthy Controls

Background and purpose: Degenerative change of the corpus callosum might serve as a clinically useful surrogate marker for net pathological cerebral impact of diabetes type 1. We compared manual and automatic measurements of the corpus callosum, as well as differences in callosal cross-sectional area between subjects with type 1 diabetes and healthy controls. Materials and methods: This is a cross-sectional study on 188 neurologically asymptomatic participants with type 1 diabetes and 30 healthy age- and sex-matched control subjects, recruited as part of the Finnish Diabetic Nephropathy Study. All participants underwent clinical work-up and brain MRI. Callosal area was manually measured and callosal volume quantified with FreeSurfer. The measures were normalized using manually measured mid-sagittal intracranial area and volumetric intracranial volume, respectively. Results: Manual and automatic measurements correlated well (callosal area vs. volume: rho = 0.83, p <0.001 and mid-sagittal area vs. intracranial volume: rho = 0.82, p <0.001). We found no significant differences in the callosal measures between cases and controls. In type 1 diabetes, the lowest quartile of normalized callosal area was associated with higher insulin doses (p = 0.029) and reduced insulin sensitivity (p = 0.033). In addition, participants with more than two cerebral microbleeds had smaller callosal area (p = 0.002). Conclusion: Manually measured callosal area and automatically segmented are interchangeable. The association seen between callosal size with cerebral microbleeds and insulin resistance is indicative of small vessel disease pathology in diabetes type 1.Peer reviewe

Glycemic control is not related to cerebral small vessel disease in neurologically asymptomatic individuals with type 1 diabetes

Aims To determine if medium- and long-term blood glucose control as well as glycemic variability, which are known to be strong predictors of vascular complications, are associated with underlying cerebral small vessel disease (cSVD) in neurologically asymptomatic individuals with type 1 diabetes. Methods A total of 189 individuals (47.1% men; median age 40.0, IQR 33.0-45.2 years) with type 1 diabetes (median diabetes duration of 21.7, IQR 18.3-30.7 years) were enrolled in a cross-sectional retrospective study, as part of the Finnish Diabetic Nephropathy (FinnDiane) Study. Glycated hemoglobin (HbA(1c)) values were collected over the course of ten years before the visit including a clinical examination, biochemical sampling, and brain magnetic resonance imaging. Markers of glycemic control, measured during the visit, included HbA(1c), fructosamine, and glycated albumin. Results Signs of cSVD were present in 66 (34.9%) individuals. Medium- and long-term glucose control and glycemic variability did not differ in individuals with signs of cSVD compared to those without. Further, no difference in any of the blood glucose variables and cSVD stratified for cerebral microbleeds (CMBs) or white matter hyperintensities were detected. Neither were numbers of CMBs associated with the studied glucose variables. Additionally, after dividing the studied variables into quartiles, no association with cSVD was observed. Conclusions We observed no association between glycemic control and cSVD in neurologically asymptomatic individuals with type 1 diabetes. This finding was unexpected considering the large number of signs of cerebrovascular pathology in these people after two decades of chronic hyperglycemia and warrants further studies searching for underlying factors of cSVD.Peer reviewe

Endothelial Dysfunction is Associated With Early-Onset Cryptogenic Ischemic Stroke in Men and With Increasing Age

Background The aim of this study was to assess the association between endothelial function and early-onset cryptogenic ischemic stroke (CIS), with subgroup analyses stratified by sex and age groups. Methods and Results We prospectively enrolled 136 consecutive patients aged 18 to 49 years (median age, 41 years; 44% women) with a recent CIS and 136 age- and sex-matched (+/- 5 years) stroke-free controls. Endothelial function was measured with an EndoPAT 2000 device and analyzed as tertiles of natural logarithm of reactive hyperemia index with lower values reflecting dysfunction. We used conditional logistic regression adjusting for age, education, hypertension, diabetes mellitus, dyslipidemia, current smoking, heavy drinking, obesity, and diet score to assess the independent association between endothelial function and CIS. Patients in the lowest tertile of natural logarithm of reactive hyperemia index were more often men and they more frequently had a history of dyslipidemia; they were also more often obese, had a lower diet score, and lower high-density lipoprotein cholesterol. In the entire cohort, we found no association in patients with endothelial function and CIS compared with stroke-free controls. In sex- and age-specific analyses, endothelial dysfunction was associated with CIS in men (adjusted odds ratio [OR], 3.50 for lowest versus highest natural logarithm of reactive hyperemia index tertile; 95% CI, 1.22-10.07) and in patients >= 41 years (OR, 5.78; 95% CI, 1.52-21.95). These associations remained significant when dyslipidemia was replaced with the ratio of total to high-density lipoprotein cholesterol. Conclusions Endothelial dysfunction appears to be an independent player in early-onset CIS in men and patients approaching middle age.Peer reviewe

Markers of early vascular aging are not associated with cryptogenic ischemic stroke in the young : A case-control study

Publisher Copyright: © 2022 The Author(s)Background and Purpose: We aimed to assess the association between covert atherosclerosis, arterial stiffness, and early-onset cryptogenic ischemic stroke (CIS) in a prospective case-control study. Methods: We enrolled 123 young CIS patients (median age 41 years; 42% women) and 123 age- and sex-matched controls. Carotid intima-media thickness (CIMT), Augmentation Index (AIx), central pulse wave velocity (PWV), and subendocardial viability ratio (SEVR) were compared between patients and controls. Conditional logistic regression was used adjusting for age, systolic blood pressure, diastolic blood pressure, current smoking, total cholesterol/high-density lipoprotein cholesterol (Total-C/HDL-C) ratio, and glycated albumin to assess the independent association between CIMT, arterial stiffness and CIS. Results: Patients with higher CIMT and PWV were older, more often men and they had more frequently well-documented risk factors, lower HDL and higher Total-C/HDL-C ratio compared to other tertiles. In univariate comparisons, we found no differences between patients and controls regarding CIMT, AIx, or PWV. In the entire cohort, patients had a significantly lower SEVR compared to controls (146.3%, interquartile range [IQR] 125.7-170.3 vs. 158.0%, IQR 141.3-181.0, P=0.010). SEVR was lower also in women compared to their controls (132.0%, IQR 119.4-156.1 vs. 158.7%, IQR 142.0-182.8, P=0.001) but no significant difference appeared between male patients and male controls. However, after adjusting for comorbidities and laboratory values these significant differences were lost (odds ratio [OR] 1.52, 95% confidence interval [CI] 0.47-4.91) in the entire cohort and OR 3.89, 95% CI 0.30-50.80 in women). Conclusions: Higher CIMT and PWV were associated to higher age, male sex, and several well-documented cardiovascular risk factors. However, in this study we could not prove that either covert atherosclerosis or arterial stiffness contribute to pathogenesis of early-onset CIS.Peer reviewe

The role of blood pressure in risk of ischemic and hemorrhagic stroke in type 1 diabetes

Abstract Background Hypertension is one of the strongest risk factors for stroke in the general population, while systolic blood pressure has been shown to independently increase the risk of stroke in type 1 diabetes. The aim of this study was to elucidate the association between different blood pressure variables and risk of stroke in type 1 diabetes, and to explore potential nonlinearity of this relationship. Methods We included 4105 individuals with type 1 diabetes without stroke at baseline, participating in the nationwide Finnish Diabetic Nephropathy Study. Mean age at baseline was 37.4 ± 11.9 years, median duration of diabetes 20.9 (interquartile range 11.5–30.4) years, and 52% were men. Office systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured. Based on these pulse pressure (PP) and mean arterial pressure (MAP) were calculated. Strokes were classified based on medical and autopsy records, as well as neuroimaging. Cox proportional hazard models were performed to study how the different blood pressure variables affected the risk of stroke and its subtypes. Results During median follow-up time of 11.9 (9.21–13.9) years, 202 (5%) individuals suffered an incident stroke; 145 (72%) were ischemic and 57 (28%) hemorrhagic. SBP, DBP, PP, and MAP all independently increased the risk of any stroke. SBP, PP, and MAP increased the risk of ischemic stroke, while SBP, DBP, and MAP increased the risk of hemorrhagic stroke. SBP was strongly associated with stroke with a hazard ratio of 1.20 (1.11–1.29)/10 mmHg. When variables were modeled using restricted cubic splines, the risk of stroke increased linearly for SBP, MAP, and PP, and non-linearly for DBP. Conclusions The different blood pressure variables are all independently associated with increased risk of stroke in individuals with type 1 diabetes. The risk of stroke, ischemic stroke, and hemorrhagic stroke increases linearly at blood pressure levels less than the current recommended treatment guidelines