Type 2 Diabetes: Platelets and Long-Term Metabolic Control as Estimated from Glycosylated Haemoglobin (HbA1c).

In type 2 diabetes, platelets are likely affected by impaired long-term glycaemic control, but such pathophysiological links are poorly understood. This study thus compares platelet reactivity (i.e. agonist-evoked platelet reactions) in vitro with glycosylated haemoglobin (HbA1c), a measure commonly used for monitoring long-term metabolic control of type 2 diabetes. Elders with type 2 diabetes (n = 35) were divided according to HbA1c into groups (HbA1c-low and high) consisting of 17 and 18 subjects, respectively. For estimating mitochondria disintegration, a flow cytometer determined mitochondrial transmembrane potentials after whole blood agonist stimulation. The activating agents used were α-thrombin (10 µM) and collagen (0.15 µg/mL). The same apparatus analysed the fibrinogen receptor activity, lysosomal exocytosis (surface lysosomal-associated membrane protein 1), and platelet procoagulant characteristics (membrane-attached annexin V) after stimulation. In type 2 diabetes, after in vitro agonist stimulation, platelet mitochondria injury was higher in the HbA1c-high group. The fibrinogen receptor, lysosomal secretion, and the creation of procoagulant platelets proved to be uninfluenced by HbA1c.

Illness beliefs among patients with chronic widespread pain - associations with self-reported health status, anxiety and depressive symptoms and impact of pain.

BACKGROUND: Chronic widespread pain (CWP) is a disabling condition associated with a decrease in health. Illness beliefs are individual and are acquired during life. Constraining beliefs may prevent patients from regaining health. Understanding these patients' illness beliefs may be a way to improve the health care they are offered. The aim of this study was to describe illness beliefs among patients with CWP and associations with self-reported health, anxiety and depressive symptoms, and impact of pain. METHOD: In this cross-sectional study, questionnaires were sent by mail to 330 patients including socio-demographic information, the Illness Perception Questionnaire (IPQ-R), the Short-Form General Health Survey (SF-36) and the Hospital Anxiety and Depression Scale (HADS). Data were analysed using descriptive statistics, non-parametric tests and linear regression analyses. RESULTS: Patients experienced and related a high number of symptoms to CWP (mean (SD) 9 (3)). The patients believed their illness to be long lasting, to affect their emotional well being, and to have negative consequences for their lives. Some 72% reported having severe or very severe pain, and impact of pain according to SF-36 was negatively correlated to several illness beliefs dimensions, anxiety- and depressive symptoms. In regression analyses, the Identity, Consequences and Personal control dimensions of IPQ-R and Anxiety- and Depressive symptoms explained 32.6-56.1% of the variance in the two component scores of SF-36. CONCLUSION: Constraining illness beliefs in patients with CWP are related to worse health status, especially in cases of high number of physical or mental symptoms, beliefs of negative consequences or the illness affecting them emotionally. Identification and understanding of these beliefs may reduce patients' suffering if they are taken into consideration in rehabilitation programs and in development of new evidence-based interventions aimed at increasing health in patients with CWP.

Inverse relationship between erythrocyte size and platelet reactivity in elderly.

Previous work indicates that erythrocytes (RBCs) accumulate ß-amyloid X-40 (Aß40) in individuals with Alzheimer disease (AD) and to a lesser extent in healthy elderly. The toxin damages RBCs and increases their mean corpuscular volume (MCV). Furthermore, AD platelets demonstrate lower reactivity. This study investigated interactions between RBCs and platelets. Older individuals with moderate hypertension (n = 57) were classified into two groups, depending on MCV in whole blood: The MCVhigh group comprised individuals with higher MCV (n = 27; 97 ± 3(SD) fl) and MCVlow group had relatively lower MCV (n = 30; 90 ± 3(SD) fl). Flow cytometry was used to determine platelet reactivity, i.e., the surface binding of fibrinogen after provocation. Adenosine diphosphate (ADP) and a thrombin receptor-activating protein (TRAP-6) were used as agonists. Subsequently, blood cells were divided according to density into 17 subfractions. Intra-RBC Aß40 content was analyzed and in all platelet populations surface-bound fibrinogen was determined to estimate platelet in vivo activity. We found Aß40 inside RBCs of approximately 50% of participants, but the toxin did not affect MCV and platelet reactivity. In contrast, MCV associated inversely with platelet reactivity as judged from surface-attached fibrinogen after ADP (1.7 µmol/L) (p < 0.05) and TRAP-6 provocation (57 µmol/L (p = 0.01) and 74 µmol/L (p < 0.05)). In several density fractions (nos. 3, 4, 8, 11-13 (p < 0.05) and nos. 5-7 (p < 0.01)) MCV linked inversely with platelet-attached fibrinogen. In our community-dwelling sample, enhanced MCV associated with decreased platelet reactivity and lower in vivo platelet activity. It resembles RBCs and platelet behavior in AD-type dementia.

Platelets and acute cerebral infarction.

Stroke is worldwide a leading cause of death and disability. Its etiology is regarded as heterogeneous. Platelets are implicated in its pathophysiology, but our understanding of their specific role is incomplete. Only sparse and conflicting information exists about platelet reactivity and activity in acute stroke. Some scientists take the view that platelets activate in conjunction with acute cerebral infarctions. Others put forward evidence corroborating the contrary notion. Increased soluble P-selectin as a sign of platelet and/or endothelial activity seems to be a feature of the disease. The latter point of view is opposed by other researchers. Due to these conflicting opinions, this study is devoted to platelet characteristics in acute cerebral infarctions. We studied subjects (n = 72; age 74 ± 10(SD) years; 31 females) having acute stroke. As controls served atrial fibrillation (AF) patients (n = 58; age 69 ± 7(SD) years; 12 females) subject to electrical cardioversion, a flow cytometer was put to use for measuring platelet reactivity and activity. After agonist provocation, both platelet bound P-selectin and fibrinogen were employed as estimates of platelet reactivity. Dilutions of a thrombin-receptor-activating peptide (TRAP-6) (74 and 57 µmol/l) (P-selectin and fibrinogen) and ADP (8.5 and 1.7 µmol/l) (fibrinogen only) were put to use as platelet agonists. Membrane-bound P-selectin without agonist stimulation served as a measure of in vivo platelet activation. Soluble P-selectin, as determined from a commercial ELISA, was used to assess platelet and/or endothelial activity. In acute stroke neither platelet-bound P-selectin nor fibrinogen after stimulation, i.e. reactivity, differed from AF controls. In contrast, lower platelet activity as judged from surface attached and circulating P-selectin without agonist stimulation proved to be a feature of cerebral infarctions. The p-values were p < 0.001 and p < 0.01, respectively. It is concluded that acute stroke is not associated with platelet reactivity platelets circulate less activated during the disease. It is evident that the mechanisms reflecting platelet reactivity and activity being investigated in this study play minor roles in stroke pathophysiology. New powerful platelet inhibitory drugs are currently introduced. To avoid major bleeding studies on platelet, behavior in acute stroke are necessary before including these medications in stroke treatment protocols.

Low-density platelet populations demonstrate low in vivo activity in sporadic Alzheimer disease.

Platelets contain a substantial quantity of amyloid-precursor protein (APP) and ß-amyloid. However, despite the large importance of APP and ß-amyloid to dementia, little is known about platelets in sporadic Alzheimer dementia (AD). Furthermore, platelet heterogeneity influences human pathology and has been described to affect the progression of AD. This study investigated AD platelets with respect to density diversity and in vivo activity associated with density sub-fractions. We included 39 AD patients and used, as controls, 22 elderly individuals without apparent memory disorder. A continuous Percoll™ gradient covering the density span 1.04-1.09 kg/l provided the basis to divide platelets of whole blood into density fractions (n = 16). All platelet populations were evaluated accordingly. Platelet counts were determined electronically. A flow-cytometer was put to use to measure surface-bound fibrinogen as a measure of platelet in vivo activity. Samples obtained from patients diagnosed with sporadic AD contained platelets (fractions numbers 4-16) that circulated with significantly less surface-bound fibrinogen, i.e., their platelet activation in vivo was reduced, compared with controls. In particular, highly significant differences (p < 0.001) were obtained for the six less dense platelet populations (fractions numbers 11-16) when comparing sporadic AD with controls. In contrast, the densest AD platelets in fractions numbers 1-3 did not differ significantly from control cells with respect to in vivo platelet-bound fibrinogen. It is concluded that sporadic AD is characterized by lower density platelet populations that, while circulating, exhibited reduced activation. The clinical significance of this finding is unclear but these results suggest the importance of platelet heterogeneity in dementia as a topic for further investigation.

Atrial fibrillation and platelet reactivity.

BACKGROUND: The impact of atrial fibrillation (AF) upon platelet reactivity has not been investigated. METHODS: Subjects were 33 individuals with AF who consented to elective electrical cardioversion (ECV) immediately before ECV determination of surface-bound fibrinogen after stimulation i.e. platelet reactivity was carried out. A flow cytometer was employed. ADP (1.7 and 8.5 µmol/L) and a thrombin receptor activating peptide (54 and 74 µmol/L) were used as agonists. The analyses were repeated after 26±8(SD) months. RESULTS: Compared to day 1 subjects with AF (n=18) had a trend towards lower platelet reactivity at study end. It reached significance when using 1.7 µmol/L ADP. In contrast, after 26±8(SD) months sinus rhythm (SR) (n=15) was associated with significant lower reactivity with all agonists. CONCLUSION: After 26±8(SD) months patients returning with AF had higher platelet reactivity than those who remained with SR.

Interleukin-6 and neutrophils are associated with long-term survival after acute myocardial infarction.

BACKGROUND: Assessing acute myocardial infarction (MI) with respect to long-term survival is not easy. Authorities in the field suggest that inflammation predicts short-range (up to 17 months) coronary death. It is not known whether long-term survival is associated with the inflammatory response. In this study, we evaluate the relationships between survival for more than 8 years and inflammation, i.e., circulating interleukin-6 (IL-6) and neutrophil counts, in acute MI. METHODS: Patients with ST-segment elevation MIs (STEMI; n=33) and non-ST-segment MIs (non-STEMI; n=39) in 1996 were included in the study. All STEMI patients received thrombolytic therapy. Acute coronary angiography was not an option. Determination of IL-6 and neutrophils was carried out within 24 h after commencement of pain. The subjects were followed for more than 8 years (until December 31, 2005) using the national death registry. Inflammatory markers at the time of MI were compared with long-term survival (n=35). RESULTS: At the time of acute MI, survivors for more than 8 years proved to have lower IL-6 (p<0.01) and decreased neutrophil counts (p<0.05). The differences remained (p<0.01 for both markers) when excluding deaths (n=11) occurring in 1996 and 1997. Subsequently, the subjects were divided into two equally sized groups, depending on their IL-6 values at the beginning of the study. As expected, a lower IL-6 was associated with a more favorable long-term prognosis (p<0.01). CONCLUSIONS: Circulating IL-6 predicts long-term survival after acute MI. Neutrophils appear to have prognostic value as well.

Elevated platelet reactivity in stable angina pectoris without significant coronary flow obstruction.

BACKGROUND: There are many different causes of angina pectoris without significant coronary flow obstruction in major coronary arteries. Examples include Prinzmetal angina and small vessel atherosclerotic disease. METHODS: We investigated individuals with stable angina pectoris subject to elective coronary angiography. To keep the study group as homogeneous as possible, patients with diabetes mellitus were excluded. Subjects with normal coronary angiograms (n = 13) or insignificant (< 50%) coronary flow obstruction(s) (n = 4) were grouped together. The remaining cohort (n = 96) with at least one significant (> or = 50%) flow obstruction in at least one major coronary artery served as controls. RESULTS: Before angiography, platelet activity in vitro on stimulation with a thrombin-receptor activating peptide (TRAP-6) (57 micromol/l and 74 micromol/l) and ADP (1.7 micromol/l and 8.5 micromol/l) was determined. Angina pectoris individuals without significant flow obstruction in major coronary arteries had enhanced platelet reactivity both when stimulated with TRAP-6 and ADP (P < 0.01 for both TRAP-6 concentrations and P < 0.05 for both ADP concentrations, respectively. CONCLUSIONS: It is concluded that angina pectoris without significant flow impediment in major epicardial arteries is associated with augmented platelet reactivity.

Inverse relationships between coronary blood flow obstruction and platelet reactivity in stable angina pectoris.

This study investigates relationships between platelet reactivity and coronary blood flow obstruction in stable angina pectoris. Consented were 36 patients with single-vessel disease. The subjects were divided into two groups. One group (n=14) had less severe (<=80%) and the second group (n=22) had severe coronary flow impairment (90%). Before elective coronary angiography platelet in vitro reactivity in venous whole blood was determined using a flow cytometry technique. A thrombin-receptor activating peptide (TRAP-6) (0.77 and 0.06 g/l) and ADP (8.5 and 1.7 micromol/l) were used to activate platelets. The number of fibrinogen positive cells (%) i.e., activated platelets after stimulation was employed as experimental parameter. Less severe flow obstruction was associated with more reactive platelets. When stimulating with 0.77 g/l TRAP-6 the number of activated platelets was 64+/-15 (SD)%. The corresponding value for the group with severe flow obstruction was 40+/-17(SD)%. The difference is significant (P<0.001). 0.06 g/l TRAP-6 yielded similar results (P<0.01). Also when using 8.5 micromol/l ADP to challenge platelets less severe flow obstruction was associated with enhanced reactivity (P<0.01). 1.7 micromol/l ADP generated comparable results (P<0.05). Thus, in stable angina pectoris coronary flow obstruction is inversely related to platelet reactivity.

Relationships between platelets and inflammatory markers in rheumatoid arthritis.

AIM OF THE STUDY: To investigate platelets and different inflammatory markers in conjunction with a substantial inflammatory reaction. We used individuals with active rheumatoid arthritis (RA) as an experimental cohort. METHODS: We selected 16 patients with active RA having at least one affected joint. On day 1, platelet and neutrophil counts together with C-reactive protein (CRP) were determined. We further analysed platelet volume (MPV) and plasma levels of thrombopoietin (TPO), P-selectin, myeloperoxidase and interleukin 6 (IL-6). After 2 years when all patients failed to show any swollen joints all analyses were repeated. RESULTS AND CONCLUSIONS: As expected platelet count, CRP and IL-6 were elevated in active RA. The measures correlated with each other thus reflecting the same characteristic of the inflammatory response. The neutrophil count, MPV and myeloperoxidase also mirror disease activity. They failed to correlate with other activity markers thus providing unique information. MPV and myeloperoxidase on day 1 correlated with recovery values. Therefore, they could be suitable to use when following the inflammatory reaction over a long period of time.

Chlamydia pneumoniae IgG and the severity of coronary atherosclerosis.

BACKGROUND: The aim of this study was to compare Chlamydia pneumoniae IgG and the extent of coronary atherosclerosis. METHODS: We investigated 92 patients with stable angina pectoris who underwent coronary angiography to assess chest pain. Before angiography, C. pneumoniae IgG was analyzed. The number of major coronary arteries (1-3) having at least one diameter narrowing (>/=50%) stenosis was determined. The patients were divided into two groups of equal size, according to C. pneumoniae IgG levels. One group included individuals with C. pneumoniae IgG levels exceeding 46 enzyme-immuno-units (EIU)/L and the other consisted of subjects with IgG concentrations below 46 EIU/L. RESULTS: Subjects with higher antibody concentrations had a more severe disease. The number of diseased arteries was 2.1+/-0.8 (S.D.) and 1.4+/-0.6 (S.D.) for the two groups, respectively. The difference is highly significant (p<0.0001). CONCLUSIONS: This study suggests a causative relationship between C. pneumoniae IgG and the degree of coronary atherosclerosis. It does not, however, prove causality.

Identification of low-density platelet populations with increased reactivity and elevated alpha-granule content.

The present study examines biochemical and functional characteristics of platelet density subpopulations together with their ability to mobilise intracellular fibrinogen when activated. Platelets from three healthy volunteers were investigated. The total platelet population was separated according to density in a linear Percoll gradient in a plasma-free milieu containing EDTA that binds soluble Ca(2+). Subsequently, platelets from each individual were divided according to density into 11 or 12 aliquots. In all fractions, we determined platelet count, intracellular P-selectin and the ADP-evoked platelet fibrinogen binding as a measure of platelet reactivity together with the platelet dense body content. The work demonstrates that platelets use stored intracellular fibrinogen when activated. It also shows that the platelet-fibrinogen binding can be initiated in a surrounding depleted of Ca(2+) and fibrinogen. Moreover, the study demonstrates subpopulations of light platelets having increased reactivity and more alpha-granules but less dense bodies. The biological significance of the findings needs to be elucidated.

Individual variations of platelet inhibition after loading doses of clopidogrel.

OBJECTIVE: To investigate individual variations of platelet inhibition after clopidogrel-loading doses. SETTING: Department of Cardiology, Linköping University Hospital, Linköping, Sweden. SUBJECTS: Individuals with stable angina pectoris (n = 18) subject to percutaneous coronary interventions (PCI) and subsequent stenting were investigated. METHODS AND EXPERIMENTAL PROTOCOL: A 300-mg clopidogrel loading dose was administrated immediately after stenting (day 1) followed by an additional 75 mg clopidogrel after 24 h (day 2). The ADP-evoked platelet fibrinogen binding was analysed to estimate platelet reactivity immediately before angiography and on day 2. A flow cytometry technique was used with two ADP solutions (final concentrations 0.6 and 1.7 micromol L-1) employed as platelet activating agents. Soluble P-selectin was used as a marker of platelet activity. RESULTS: When using 1.7 micromol L-1 ADP to activate platelets four individuals had a strong inhibition (i.e. platelet reactivity <10% of the day 1-value day 2). In contrast, five patients demonstrated a weak inhibition (i.e. platelet reactivity >60% of the day 1-value day 2). Similar results were obtained when using 0.6 micromol L-1 ADP as a platelet-activating agent. Clopidogrel, however, fails to suppress platelet activity as estimated from soluble P-selectin. CONCLUSIONS: Clopidogrel evoked platelet inhibition exhibits a considerable individual heterogeneity. Some individuals only had weak responses whereas others displayed strong platelet inhibition. The present flow cytometry technique appears suitable for identifying patients with abnormal reactions after clopidogrel exposure.

Evidence that Chlamydia pneumoniae affects platelet activity in patients with acute myocardial infarction and ST-segment elevations.

This study concerns platelet activity at myocardial infarctions and possible relationships with Chlamydia pneumoniae seroreactivity. Fourteen patients with acute myocardial infarction and ST-segment elevations were enrolled. They all received thrombolytic therapy. The subjects were examined within 24 h after hospital admission (Day 1) and after 6 months of recovery. On Day 1, C. pneumoniae IgM antibody titres were analysed and on Day 1 and during recovery C. pneumoniae IgG and soluble P-selectin were determined. P-selectin was used to estimate platelet activation. C. pneumoniae IgM titres at the infarction were closely related to both Day 1 IgG titres (r = 0.6; p < 0.05) and to IgG levels after 6 months (r = 0.8; p < 0.01). These results indicate a possible reactivation of a chronic infection. C. pneumoniae IgM was related to platelet activation. The correlation coefficient was r = 0.7 (p < 0.01) when comparing IgM titres with Day 1 plasma P-selectin. A similar relationship was found when comparing IgM and recovery P-selectin (r = 0.8; p < 0.01). The pathogen appears to contribute to platelet responses occurring during myocardial infarctions with ST-segment elevations. It is concluded that an ongoing reactivation of a chronic infection is related to increased platelet activity.

Inverse relationship between platelet density and reactivity alterations at coronary angiography.

This work investigates relationships between platelet density and reactivity. 21 individuals subject to coronary angiography were studied. Peak platelet density was analyzed using a newly developed electronic device. The apparatus measures light transmission through test tubes containing density-separated platelets, thus allowing an estimation of the platelet distribution in the gradient. A flow cytometry technique was used for determining platelet reactivity after stimulating with ADP. Platelet counts, mean platelet volumes, peak platelet density and platelet reactivity were determined immediately before (day 1) and 24 h after cardiac catheterization (day 2). For all parameters changes during the day of angiography were compared with platelet density alterations. The subjects were divided into two groups according to density changes at angiography. Group 1 individuals showed density alterations (i.e. day 2 - day 1 value) > or = -8 x 10(-5) kg/l. In contrast, group 2 subjects either displayed density changes < -8 x 10(-5) kg/l or grossly disturbed platelet density patterns on day 2. Before angiography both groups had similar platelet counts and volumes. Then platelet reactivity when stimulating with ADP did not differ significantly between the two groups. After angiography, the number of fibrinogen-positive cells when stimulating with ADP rose by 6 +/- 8% for group 2 patients. The corresponding figure for group 1 was -1 +/- 6%. The difference was significant (p = 0.01). No such relationships were found when comparing density alterations and changes of platelet counts and volumes. We conclude that in this study platelet density alterations at coronary angiography are inversely related to variations of platelet reactivity.

The use of platelet density and volume measurements to estimate the severity of pre-eclampsia.

BACKGROUND: This study evaluated whether it is possible to estimate the severity of pre-eclampsia through in vitro measurements of platelet and granulocyte parameters. EXPERIMENTAL PROTOCOL: Eighteen pre-eclamptic women in the third-trimester of pregnancy and 11 women in the third-trimester of normal pregnancies were included in the study. Three to 12 months after delivery, 15 patients with pre-eclampsia and all the subjects with normal pregnancies were re-examined. Before delivery, peak platelet density was determined using a specially designed apparatus. Before and 3-12 months after delivery the following were measured: platelet counts, mean platelet volume and neutrophil and monocyte counts. Furthermore, circulating P-selectin, interleukin-6 and myeloperoxidase were determined to estimate platelet, monocyte and granulocyte activities, respectively. RESULTS: Compared to their results after delivery, pre-eclamptic females demonstrated lower platelet counts (P < 0.001) and raised mean platelet volumes (P < 0.01). Both pre-eclamptic women (P < 0.01) and normal pregnancies (P < 0.05) demonstrated elevated soluble P-selectin at pregnancy. Then pre-eclamptic women had advanced neutrophil counts (P < 0.01) but normal pregnancies showed a similar phenomenon (P < 0.001). Interleukin-6 remained normal during pregnancy. Plasma myeloperoxidase levels were lower both in pre-eclampsia (P < 0.05) and in normal pregnancies (P < 0.001). In pre-eclampsia elevated blood pressure was related to higher mean platelet volumes (P < 0.05). Furthermore, a group of pre-eclamptic females whose platelets had disturbed density distribution displayed elevated mean platelet volumes (P < 0.01). CONCLUSIONS: The present work demonstrates considerable platelet alterations in pre-eclampsia. We failed to show granulocyte involvement in the pathogenesis of the disease. Severe pre-eclampsia is related to elevated mean platelet volumes. The latter parameter is associated with disturbed density distribution. It appears possible to estimate disease severity from measurements of platelet density and volume.

Elevated inflammatory parameters are associated with lower platelet density in acute myocardial infarctions with ST-elevation.

OBJECTIVE: Platelets and granulocytes play important roles in coronary disorders. We therefore, investigated platelet and granulocyte alterations in myocardial infarctions (MIs). PATIENTS AND STUDY DESIGN: A total of 36 individuals having MI with raised ST-segments who were receiving thrombolytic therapy were studied. Sampling was carried out after thrombolysis within 24 h after hospital admission. After 3 to 6 months of recovery, 25 patients were reinvestigated. At the infarction, peak platelet density was determined using a special designed computerised apparatus. In addition, we did counts on platelets, neutrophils and monocytes. Moreover, plasma levels of soluble P-selectin, myeloperoxidase and interleukin 6 were determined to estimate the degree of platelet, neutrophil and monocyte activation, respectively. Peak platelet density was analysed at the MI. All other parameters were determined at the acute event and at recovery. RESULTS: At the MI, compared to the recovery, platelet counts were lower (P<0.001). In addition, increased neutrophil counts (P<0.001), elevated monocyte counts (P<0.001), enhanced myeloperoxidase (P<0.001) and interleukin 6 (P<0.001) levels were demonstrated. We failed to show elevated soluble P-selectin. Compared to individuals with ST-segment elevations and low platelet density (less than or = 1.058 kg/l), patients having peak platelet densities >1.058 kg/l displayed lower neutrophil counts (P<0.01) and decreased interleukin 6 levels (P<0.01). Furthermore, we demonstrate that individuals with higher inflammatory response at the MI had higher neutrophil (r = 0.6; P<0.01) and higher monocyte counts (r = 0.6; P<0.001) at recovery. CONCLUSION: W conclude that MI is associated with an inflammatory response. However, a subgroup of patients having MI with ST-elevations and low peak platelet density was identified. Compared to subjects with higher platelet density, they had more severe inflammatory characteristics. The differences persisted during recovery.