Aase Handberg

The Alzheimer's Association external quality control program for cerebrospinal fluid biomarkers.

The cerebrospinal fluid (CSF) biomarkers amyloid β (Aβ)‐42, total‐tau (T‐tau), and phosphorylated‐tau (P‐tau) demonstrate good diagnostic accuracy for Alzheimers disease (AD). However, there are large variations in biomarker measurements between studies, and between and within laboratories. The Alzheimers Association has initiated a global quality control program to estimate and monitor variability of measurements, quantify batch‐to‐batch assay variations, and identify sources of variability. In this article, we present the results from the first two rounds of the program.

Identification of the Oxidized Low-Density Lipoprotein Scavenger Receptor CD36 in Plasma A Novel Marker of Insulin Resistance

Background— Macrophage CD36 scavenges oxidized low-density lipoprotein, leading to foam cell formation, and appears to be a key proatherogenic molecule. Increased expression of CD36 has been attributed to hyperglycemia and to defective macrophage insulin signaling in insulin resistance. Premature atherosclerosis is the major cause of morbidity and mortality in type 2 diabetes. Here, we report the identification of a soluble form of CD36 (sCD36) in plasma and hypothesize that sCD36 would be elevated in patients with type 2 diabetes and insulin resistance. Methods and Results— sCD36 in plasma was demonstrated by immunopurification and Western blotting. We established ELISA assays to determine sCD36 in plasma and measured sCD36 in obese type 2 diabetic patients, obese nondiabetic relatives, and obese and lean control subjects. sCD36 was markedly elevated in type 2 diabetic patients compared with both lean (5-fold) and obese (2- to 3-fold) control subjects. There was a strong, inverse correlation between sCD36 and insulin-stimulated glucose disposal and a direct correlation with fasting plasma glucose, fasting insulin, and body mass index. Conclusions— Our study demonstrates sCD36 in plasma for the first time. sCD36 is highly related to risk factors of accelerated atherosclerosis in type 2 diabetes such as insulin resistance and glycemic control, and we propose that sCD36 might represent a marker of the metabolic syndrome and a potential surrogate marker of atherosclerosis.

Insulin resistance in skeletal muscles in patients with NIDDM.

Skeletal muscles in patients with non-insulin-dependent diabetes mellitus (NIDDM) are resistant to insulin; i.e., the effect of insulin on glucose disposal is reduced compared with the effect in control subjects. This defect has been found to be localized to the nonoxidative pathway of glucose disposal; hence, the deposition of glucose, as glycogen, is abnormally low. This defect may be inherited, because it is present in first-degree relatives to NIDDM patients two to three decades before they develop frank diabetes mellitus. The cellular defects responsible for the abnormal insulin action in NIDDM patients is reviewed in this article. The paper focuses mainly on convalent insulin signaling. Insulin is postulated to stimulate glucose storage by initiating a cascade of phosphorylation and dephosphorylation events, which results in dephosphorylation and hence activation of the enzyme glycogen synthase. Glycogen synthase is the key enzyme in regulation of glycogen synthesis in the skeletal muscles of humans. This enzyme is sensitive to insulin, but in NIDDM patients it has been shown to be completely resistant to insulin stimulation when measured at euglycemia. The enzyme seems to be locked in the glucose-6-phosphate (G-6-P)-dependent inactive D-form. This hypothesis is favored by the finding of reduced activity of the glycogen synthase phosphatase and increased activity of the respective kinase CAMP-dependent protein kinase. A reduced glycogen synthase activity has also been found in normoglycemic first-degree relatives of NIDDM patients, indicating that this abnormality precedes development of hyperglycemia in subjects prone to develop NIDDM. Therefore, this defect may be of primary genetic origin. However, it does not appear to be a defect in the enzyme itself, but rather a defect in the covalent activation of the enzyme system. Glycogen synthase is resistant to insulin but may be activated allosterically by G-6-P. This means that the defect in insulin activation can be compensated for by increased intracellular concentrations of G-6-P. In fact, we found that both hyperinsulinemia and hyperglycemia are able to increase the G-6-P level in skeletal muscles. Thus, insulin resistance in the nonoxidative pathway of glucose processing can be overcomed (compensated) by hyperinsulinemia and hyperglycemia. In conclusion, we hypothesize that insulin resistance in skeletal muscles may be a primary genetic defect preceding the diabetic state. The cellular abnormality responsible for that may be a reduced covalent insulin activation of the enzyme glycogen synthase. The compensation results in nearnormalization of glycogen synthesis, but the price diabetic subjects must pay to obtain this is hyperglycemia.

Variation in Absorption of NPH Insulin Due to Intramuscular Injection

To evaluate the importance of accidental intramuscular injection of NPH insulin, we measured disappearance rates of 125I-labeled NPH insulin (Protaphane) from subcutaneous and intramuscular injection sites in the thighs of 11 insulin-dependent diabetes mellitus patients. Both subcutaneous and intramuscular absorption rates were measured four times in each patient. NPH insulin was absorbed much faster when given intramuscularly than when given subcutaneously (T50% = 5.3 vs. 10.3 h, P < 0.0001). The intrapatient (day-to-day) coefficient of variation (C.V.) of T50% values (C.V. T50%) for subcutaneously injected NPH insulin in this study, where all injections were guided by ultrasound determination of the subcutaneous fat layer, was 18.4%. Intrapatient variation of absorption was significantly lower for subcutaneously than intramuscularly injected NPH insulin (C.V. T50% = 18.4 vs. 29.8%, P < 0.01) and was also lower than interpatient variation for subcutaneously injected insulin (C.V. T50% = 18.4 vs. 50%, P < 0.0001). The faster absorption rate and shorter duration of action, together with the higher day-to-day variation in absorption, led us to conclude that intramuscular injection of NPH insulin should be avoided.

A flow cytometric method for characterization of circulating cell-derived microparticles in plasma

Background and aim Previous studies on circulating microparticles (MPs) indicate that the majority of MPs are of a size below the detection limit of most standard flow cytometers. The objective of the present study was to establish a method to analyze MP subpopulations above the threshold of detection of a new generation BD FACSAria™ III digital flow cytometer. Methods We analyzed MP subpopulations in plasma from 24 healthy individuals (9 males and 15 females). MPs were identified according to their size (<1.0-µm), by Lactadherin-FITC labelling, and by exposure of cell-specific markers. The sensitivity of the flow cytometer was tested against that of a previous-generation instrument FC500. Reproducibility of the FACSAria and our set-up was investigated, and the percentage of phosphatidylserine (PS) exposing MPs binding Lactadherin was determined. Results By using a flow cytometric approach we identified and quantitated MPs derived from platelets, monocytes, erythrocytes and endothelial cells. In addition, levels of tissue factor-positive MPs were determined. The FACSAria demonstrated improved sensitivity and increased MP detection range compared to the FC500 instrument. The reproducibility of PS+PMP and PS+MP measurements was 11.7 and 23.2%, respectively. When expressed as a percentage of total MPs, the PS-positive MP population represented 15.1±5.5%, and PS-positive MPs were significantly increased in men. Conclusion We have established a method to measure MPs above the detection limit of a new generation flow cytometer and derived from a number of cell-types in a healthy population of men and women.

Soluble CD36 in Plasma Is Increased in Patients With Symptomatic Atherosclerotic Carotid Plaques and Is Related to Plaque Instability

Background and Purpose— The risk for cardiovascular events is related to the composition and stability of an atherosclerotic plaque driven by inflammation and deposition of lipids. Scavenger receptors are a family of cell surface receptors involved in lipid uptake and inflammation. Recently, we found that soluble CD36 is increased in plasma from patients with diabetes strongly correlated with insulin resistance. Methods— We tested whether soluble CD36 is a marker of plaque stability in patients with high-grade internal carotid stenoses (n=62). The patients were classified according to plaque symptomatology and plaque echogenicity on ultrasound examination. Results— When patients were divided into 3 groups according to the latest clinical symptoms from plaques (ie, symptoms within the last 2 months [n=16], symptoms within the last 2 to 6 months [n=15], or asymptomatic [n=31]), the former group had significantly raised plasma levels of soluble CD36 as compared with the other 2 groups. In contrast, we found no differences in plasma levels of C-reactive protein, β-thromboglobulin, lipid parameters, or HbA1C between these groups. The patients with echolucent carotid plaques (n=20) tended to have higher soluble CD36 levels in plasma compared with those with echogenic/heterogenic plaque (n=39; P=0.087). By immunohistochemistry, CD36 was localized to macrophages-rich area of intima within the atherosclerotic lesion. Conclusion— We propose that sCD36 may be a marker of plaque instability and symptomatic carotid atherosclerosis, possibly at least partly as a result of CD36 release to the circulation from the foam cells within the atherosclerotic lesion.

Insulin action and long-term electrically induced training in individuals with spinal cord injuries

PURPOSE Individuals with spinal cord injuries (SCI) have an increased prevalence of insulin resistance and type 2 diabetes mellitus. In able-bodied individuals, training with large muscle groups increases insulin sensitivity and may prevent type 2 diabetes mellitus. However, individuals with SCI cannot voluntarily recruit major muscle groups, but by functional electrical stimulation (FES) they can now perform ergometer bicycle training. METHODS Ten subjects with SCI (35 +/- 2 yr (mean +/- SE), 73 +/- 5 kg, level of lesion C6--Th4, time since injury: 12 +/- 2 yr) performed 1 yr of FES cycling (30 min x d(-1), 3 d x wk(-1) (intensive training)). Seven subjects continued 6 months with reduced training (1 d x wk(-1) (reduced training)). A sequential, hyperinsulinemic (50 mU x min(-1) x m(-2) (step 1) and 480 mU x min(-1) x m(-2) (step 2)), euglycemic clamp, an oral glucose tolerance test (OGTT), and determination of GLUT 4 transporter protein in muscle biopsies were performed before and after training. RESULTS Insulin-stimulated glucose uptake rates increased after intensive training (from 4.9 +/- 0.5 mg x min(-1) x kg(-1) to 6.2 +/- 0.6 mg x min(-1) x kg(-1) (P < 0.008) (step 1) and from 9.0 +/- 0.8 mg x min(-1) x kg(-1) to 10.6 +/- 0.8 mg x min(-1) x kg(-1) (P = 0.103) (step 2)). With the reduction in training, insulin sensitivity decreased to a similar level as before training (P > 0.05). GLUT 4 increased by 105% after intense training and decreased again with the training reduction. The subjects had impaired glucose tolerance before and after training, and neither glucose tolerance nor insulin responses to OGTT were significantly altered by training. CONCLUSIONS Electrically induced bicycle training, performed three times per week increases insulin sensitivity and GLUT 4 content in skeletal muscle in subjects with SCI. A reduction in training to once per week is not sufficient to maintain these effects. FES training may have a role in the prevention of the insulin resistance syndrome in persons with SCI.

Soluble CD36 (sCD36) Clusters with Markers of Insulin Resistance, and High sCD36 Is Associated with Increased Type 2 Diabetes Risk

CONTEXT AND OBJECTIVE Soluble CD36 (sCD36) may be an early marker of insulin resistance and atherosclerosis. The objective of this prospective study was to evaluate sCD36 as a predictor of type 2 diabetes and to study its relationship with components of the metabolic syndrome (MetSy). DESIGN, SETTING, PARTICIPANTS, AND OUTCOME MEASURES: We conducted a case-referent study nested within a population-based health survey. Baseline variables included sCD36, body mass index, blood pressure, blood lipids, adipokines, inflammatory markers, and beta-cell function. A total of 173 initially nondiabetic cohort members who developed type 2 diabetes during 10 yr of follow-up were matched (1:2) with referents. Exploratory factor analysis was applied to hypothesize affiliation of sCD36 to the MetSy components. RESULTS Doubling of baseline sCD36 increases the odds ratio for diabetes development by 1.24 in the general study population and by 1.45 in the female population (P < 0.025). Comparing upper sCD36 quartiles with lower, odds ratio for diabetes was 4.6 in women (P = 0.001), 3.15 in men (P = 0.011), and 2.6 in obese individuals (P < 0.025). Multivariate analysis shows that sCD36 does not predict diabetes independent of fasting plasma glucose and insulin. Factor analysis of 15 variables generates a six-factor model explaining 66-69% of total variance, where sCD36, body mass index, insulin, proinsulin, and leptin were assigned to the obesity/insulin resistance cluster. CONCLUSIONS Upper quartile sCD36 is associated with elevated diabetes risk independent of age, gender, and obesity. Baseline sCD36 does not, however, predict diabetes independent of fasting glucose and insulin. sCD36 clusters with important markers of insulin resistance and MetSy that are key predictors of type 2 diabetes.

Plasma sCD36 is associated with markers of atherosclerosis, insulin resistance and fatty liver in a nondiabetic healthy population

Abstract.  Handberg A, Højlund K, Gastaldelli A, Flyvbjerg A, Dekker JM, Petrie J, Piatti P, Beck‐Nielsen H (Aarhus Hospital and Aalborg Hospital, Aarhus University Hospital, Aarhus, Denmark; Odense University Hospital, Odense, Denmark; Institute of Clinical Physiology, CNR Pisa, Pisa, Italy; Aarhus University Hospital, Aarhus, Denmark; Vrije Universiteit Amsterdam, Amsterdam, The Netherlands; BHF Glasgow Cardiovascular Research Centre, Glasgow, UK; and San Raffaele Institute, Milan, Italy). Plasma sCD36 is associated with markers of atherosclerosis, insulin resistance and fatty liver in a nondiabetic healthy population. J Intern Med 2012; 271: 294–304.

Long-term Delivery of Nerve Growth Factor by Encapsulated Cell Biodelivery in the Göttingen Minipig Basal Forebrain

Nerve growth factor (NGF) prevents cholinergic degeneration in Alzheimers disease (AD) and improves memory in AD animal models. In humans, the safe delivery of therapeutic doses of NGF is challenging. For clinical use, we have therefore developed an encapsulated cell (EC) biodelivery device, capable of local delivery of NGF. The clinical device, named NsG0202, houses an NGF-secreting cell line (NGC-0295), which is derived from a human retinal pigment epithelial (RPE) cell line, stably genetically modified to secrete NGF. Bioactivity and correct processing of NGF was confirmed in vitro. NsG0202 devices were implanted in the basal forebrain of Göttingen minipigs and the function and retrievability were evaluated after 7 weeks, 6 and 12 months. All devices were implanted and retrieved without associated complications. They were physically intact and contained a high number of viable and NGF-producing NGC-0295 cells after explantation. Increased NGF levels were detected in tissue surrounding the devices. The implants were well tolerated as determined by histopathological brain tissue analysis, blood analysis, and general health status of the pigs. The NsG0202 device represents a promising approach for treating the cognitive decline in AD patients.