Phospholipids are imported into mitochondria by VDAC, a dimeric beta barrel scramblase

Mitochondria are double-membrane-bounded organelles that depend critically on phospholipids supplied by the endoplasmic reticulum. These lipids must cross the outer membrane to support mitochondrial function, but how they do this is unclear. We identify the Voltage Dependent Anion Channel (VDAC), an abundant outer membrane protein, as a scramblase-type lipid transporter that catalyzes lipid entry. On reconstitution into membrane vesicles, dimers of human VDAC1 and VDAC2 catalyze rapid transbilayer translocation of phospholipids by a mechanism that is unrelated to their channel activity. Coarse-grained molecular dynamics simulations of VDAC1 reveal that lipid scrambling occurs at a specific dimer interface where polar residues induce large water defects and bilayer thinning. The rate of phospholipid import into yeast mitochondria is an order of magnitude lower in the absence of VDAC homologs, indicating that VDACs provide the main pathway for lipid entry. Thus, VDAC isoforms, members of a superfamily of beta barrel proteins, moonlight as a class of phospholipid scramblases - distinct from alpha-helical scramblase proteins - that act to import lipids into mitochondria.

An alliance between lipid transfer proteins and scramblases for membrane expansion

Membrane growth requires lipid supply, which is usually accomplished by lipid synthesis or vesicular trafficking. In the case of autophagosomes, these principles do not apply. Ghanbarpour et al. postulate that autophagosome expansion relies on non-vesicular lipid delivery from the ER, whereby the activity of a lipid transfer protein (LTP) is directly coupled to scramblase activities in the donor and acceptor bilayers¹. This new concept opens the possibility that lipid traffic is controlled by scramblases that provide not only specific docking sites for LTPs, thereby directing lipid flow, but also support their activity by overcoming barriers for lipid extraction and deposition.

Ceramides bind VDAC2 to trigger mitochondrial apoptosis

Ceramides draw wide attention as tumor suppressor lipids that act directly on mitochondria to trigger apoptotic cell death. However, molecular details of the underlying mechanism are largely unknown. Using a photoactivatable ceramide probe, we here identify the voltage-dependent anion channels VDAC1 and VDAC2 as mitochondrial ceramide binding proteins. Coarse-grain molecular dynamics simulations reveal that both channels harbor a ceramide binding site on one side of the barrel wall. This site includes a membrane-buried glutamate that mediates direct contact with the ceramide head group. Substitution or chemical modification of this residue abolishes photolabeling of both channels with the ceramide probe. Unlike VDAC1 removal, loss of VDAC2 or replacing its membrane-facing glutamate with glutamine renders human colon cancer cells largely resistant to ceramide-induced apoptosis. Collectively, our data support a role of VDAC2 as direct effector of ceramide-mediated cell death, providing a molecular framework for how ceramides exert their anti-neoplastic activity.

Membrane Solubilization by Styrene-Maleic Acid Copolymers: Delineating the Role of Polymer Length

Styrene-maleic acid (SMA) copolymers have attracted interest in membrane research because they allow the solubilization and purification of membrane-spanning proteins from biological membranes in the form of native-like nanodisks. However, our understanding of the underlying SMA-lipid interactions is hampered by the fact that SMA preparations are very polydisperse. Here, we obtained fractions of the two most commonly used SMA preparations: SMA 2:1 and SMA 3:1 (both with specified Mw ∼10 kD), with different number-average molecular weight (Mn) and styrene content. The fractionation is based on the differential solubility of styrene-maleic anhydride (SMAnh) in hexane and acetone mixtures. SMAnh fractions were hydrolyzed to SMA and added to lipid self-assemblies. It was found that SMA fractions inserted in monolayers and solubilized vesicles to a different extent, with the highest efficiency being observed for low-Mn SMA polymers. Electron microscopy and dynamic light scattering size analyses confirmed the presence of nanodisks independent of the Mn of the SMA polymers forming the belt, and it was shown that the nanodisks all have approximately the same size. However, nanodisks bounded by high-Mn SMA polymers were more stable than those bounded by low-Mn polymers, as indicated by a better retention of the native lipid thermotropic properties and by slower exchange rates of lipids between nanodisks. In conclusion, we here present a simple method to separate SMAnh molecules based on their Mn from commercial SMAnh blends, which allowed us to obtain insights into the importance of SMA length for polymer-lipid interactions.

Effectiveness and Safety of Recombinant Human Erythropoietin (r-HuEPO) in the Treatment of Anemia of Chronic Renal Failure in Non Dialysis Patients

Seventy-five non-dialized patients with chronic renal failure (CRF) and severe renal anemia were enrolled in a study, receiving r-HuEPO subcutaneously thrice weekly for 6 months. In 64 patients (85%) 7 weeks of treatment with a weekly dose of 158 U/kg were required to achieve Hb concentrations within the target range of 10 to 12 g/dl. Of the 11 patients (15%) who failed to achieve the target Hb range, none were considered to be non-responders as they were excluded for unrelated reasons prior to week 16 (8 cases), or were iron deficient (2 cases), or had bleeding complications (1 patient). Maintaining the Hb concentration at a level of 10.5 g/dl required a mean r-HuEPO dose of 92 U/kg per week. Adverse events were generally mild or moderate. The most commonly reported were hypertension (8%), viral infection/including flu-like syndrome (7%), nausea (7%), and dizziness (5%). Statistically significant increases in mean creatinine concentrations observed after 12 and 24 weeks were most likely due to the progression of renal disease. These results confirm that 50 U/kg of r-HuEPO given 3 times per week subcutaneously provide a safe and effective therapy for anemic predialysis patients.

Effects of 1,25(OH)2D3 on cardiovascular function

1,25(OH)2D3 enhances myocardial contractility with pharmacological doses from 1 to 20 micrograms within 30-60 min. dp/dt modifications induced by 1,25(OH)2D3 are dose dependent and approach linearity from 1 to 10 micrograms. The inotropic effects are not dependent on extracellular Ca2+ levels; but cellular Ca2+ influx or internal Ca2+ movement may be implied. The effect seems not related to the described 1,25(OH)2D3 receptors which implies protein de novo synthesis. A modulation on other receptor-mediated substances acting on Ca2+ movements seems probable.

A combination of galantamine and memantine modifies cognitive function in subjects with amnestic MCI

OBJECTIVES

Mild cognitive impairment (MCI) is etiologically heterogeneous, and a substantial proportion of MCI subjects will develop different dementia disorders. One subtype of this syndrome, amnestic MCI, occurs preferentially but not exclusively in prodromal AD and is characterized by defined deficits of episodic memory.

DESIGN, SETTING AND PARTICIPANTS

For a 2-year, double-blinded, placebo-controlled study MCI patients, presenting with an amnestic syndrome but not necessarily based on presumed prodromal AD were randomized.

INTERVENTION

Patients received (a) a combination of 16 mg galantamine plus 20 mg memantine, or (b) 16 mg galantamine alone or (c) placebo.

MEASUREMENTS

The primary objective was to explore the differential impact of these interventions on the progression to dementia and on cognitive changes as measured by the ADAScog.

RESULTS

After recruitment of 232 subjects, the trial was halted before reaching the planned sample size, because safety concerns arose in other studies with galantamine in MCI. This resulted in a variable treatment duration of 2-52 weeks. The statistical analysis plan was amended for studying cognitive effects of discontinuing the study medication, which was done separately for galantamine and memantine, and under double-blind conditions. There was one death, no unexpected severe adverse events, and no differences of severe adverse events between the treatment arms. The cognitive changes on the ADAScog were not different among the groups. Only for the subgroup of amnestic MCI with presumed AD etiology, a significant improvement of ADAScog score over placebo before the discontinuation of medication was observed, while amnestic MCI presumably due to other etiologies showed no cognitive changes with broad variation. Cognitive improvement was numerically larger in the combination treatment group than under galantamine alone. Patients who received placebo declined as expected. Discontinuation of galantamine, either as part of the combination regimen or as mono treatment, resulted in a transient decline of the ADAScog score in amnestic MCI of presumed AD etiology, while discontinuation of Memantine did not change the cognitive status.

CONCLUSION

In an interrupted trial with amnestic MCI subjects the combination of galantamine plus memantine were generally well tolerated. In the subgroup of MCI subjects with presumed AD etiology, a cognitive benefit of a short-term combination treatment of galantamine plus memantine was observed, and cognitive decline occurred after discontinuation of galantamine.

Soluble amyloid precursor proteins in the cerebrospinal fluid as novel potential biomarkers of Alzheimer's disease: a multicenter study

In this report, we present the results of a multicenter study to test analytic and diagnostic performance of soluble forms of amyloid precursor proteins alpha and beta (sAPP alpha and sAPP beta) in the cerebrospinal fluid (CSF) of patients with different forms of dementing conditions. CSF samples were collected from 188 patients with early dementia (mini-mental state examination >or=20 in majority of cases) and mild cognitive impairment (MCI) in 12 gerontopsychiatric centers, and the clinical diagnoses were supported by neurochemical dementia diagnostic (NDD) tools: CSF amyloid beta peptides, Tau and phospho-Tau. sAPP alpha and sAPP beta were measured with multiplexing method based on electrochemiluminescence. sAPP alpha and sAPP beta CSF concentrations correlated with each other with very high correlation ratio (R=0.96, P<0.001). We observed highly significantly increased sAPP alpha and sAPP beta CSF concentrations in patients with NDD characteristic for Alzheimer's disease (AD) compared to those with NDD negative results. sAPP alpha and sAPP beta highly significantly separated patients with AD, whose diagnosis was supported by NDD findings (sAPP alpha: cutoff, 117.4 ng ml(-1), sensitivity, 68%, specificity, 85%, P<0.001; sAPP beta: cutoff, 181.8 ng ml(-1), sensitivity, 75%, specificity, 85%, P<0.001), from the patients clinically assessed as having other dementias and supported by NDD untypical for AD. We conclude sAPP alpha and sAPP beta might be regarded as novel promising biomarkers supporting the clinical diagnosis of AD.

Amyloid beta peptides in plasma in early diagnosis of Alzheimer's disease: A multicenter study with multiplexing

We measured concentrations of Abeta peptides 1-42 and 1-40, and their ratio in plasma of patients carefully categorized clinically and neurochemically as having AD or other dementias with a newly commercially available multiplexing assay, characterized by reasonable laboratory performance (intra-assay imprecision in the range of 1.3-3.8% for Abeta1-42, and 1.8-4.1% for Abeta1-40, inter-assay imprecision for Abeta1-42, Abeta1-40, and Abeta1-42/Abeta1-40 concentration ratio in the range of 2.3-11.5%, 2.2-10.4% and 4.2-9.7%, respectively). Patients with AD or mild cognitive impairment of AD type (MCI-AD) whose clinical diagnosis was supported with CSF biomarkers (n=193) had significantly lower Abeta1-42 plasma concentrations (p<0.007), and Abeta1-42/1-40 ratios (p<0.003) compared to patients with other dementias and MCI of other types (n=64). No significant differences between persons with MCI of AD type and patients with early AD were observed, or between MCI of other types versus patients with early dementia of other types. Our findings reconfirm the hypothesis that alterations of biomarker concentrations occur early in a preclinical AD stage and that these alterations are also reflected in plasma.

A multicenter (1)H-MRS study of the medial temporal lobe in AD and MCI

OBJECTIVE

The need for biological markers of Alzheimer disease (AD) is constantly increasing. Proton magnetic resonance spectroscopy ((1)H-MRS) studies have provided consistent evidence for a reduction of the neuronal marker N-acetylaspartate (NAA) in patients with AD. Within the German Competence Network on Dementia, we conducted a (1)H-MRS study in patients with mild dementia and mild cognitive impairment (MCI) at four sites to investigate the multicenter feasibility of (1)H-MRS.

METHODS

In total, 130 patients with dementia (98 AD, 32 non-AD), 136 subjects with MCI (70 of AD type, 66 of non-AD type), and 45 unimpaired control subjects were included. Single-volume (1)H-MRS of the left medial temporal lobe was performed at long and short echo times. Metabolites were quantified and metabolic ratios were determined.

RESULTS

We found a significant reduction of NAA concentration in patients with AD as compared to healthy volunteers and compared to patients with MCI of AD type. NAA/Cr (creatine/phosphocreatine) was also lower in patients with AD compared to control subjects. NAA, choline compounds, and Cr were lower in patients with AD compared to patients with non-AD dementia.

CONCLUSIONS

We demonstrated the multicenter feasibility of proton magnetic resonance spectroscopy ((1)H-MRS) of the medial temporal lobe in mild dementia and mild cognitive impairment, which is a prerequisite for the application of (1)H-MRS in large-scale clinical trials. Since the concentration measures of the metabolites are adjusted for brain tissue volume, these findings are indicators of biochemical pathology beyond brain atrophy.

Evolution of Abeta42 and Abeta40 levels and Abeta42/Abeta40 ratio in plasma during progression of Alzheimer's disease: a multicenter assessment

OBJECTIVE

To better understand the seemingly contradictory plasma beta-amyloid (Abeta) results in Alzheimer's disease (AD) patients by using a newly developed plasma Abeta assay, the INNO-BIA plasma Abeta forms, in a multicenter study.

METHODS

A combined retrospective analysis of plasma Abeta isoforms on mild cognitive impairment (MCI) from three large cross-sectional studies involving 643 samples from the participating German and Swedish centers.

RESULTS

Detection modules based on two different amino (N)-terminal specific Abeta monoclonal antibodies demonstrated that Abeta in plasma could be reliable quantified using a sandwich immunoassay technology with high precision, even for low Abeta42 plasma concentrations. Abeta40 and Abeta42 concentrations varied consistently with the ApoE genotype, while the Abeta42/Abeta40 ratio did not. Irrespective of the decrease of the Abeta42/Abeta40 ratio with age and MMSE, this parameter was strongly associated with AD, as defined in this study by elevated hyperphosphorylated (P-tau181P) levels in cerebrospinal fluid (CSF).

CONCLUSION

A highly robust assay for repeatedly measuring Abeta forms in plasma such as INNO-BIA plasma Abeta forms might be a useful tool in a future risk assessment of AD.

Improvement of cognitive functions in chronic schizophrenic patients by recombinant human erythropoietin

Schizophrenia is increasingly recognized as a neurodevelopmental disease with an additional degenerative component, comprising cognitive decline and loss of cortical gray matter. We hypothesized that a neuroprotective/neurotrophic add-on strategy, recombinant human erythropoietin (rhEPO) in addition to stable antipsychotic medication, may be able to improve cognitive function even in chronic schizophrenic patients. Therefore, we designed a double-blind, placebo-controlled, randomized, multicenter, proof-of-principle (phase II) study. This study had a total duration of 2 years and an individual duration of 12 weeks with an additional safety visit at 16 weeks. Chronic schizophrenic men (N=39) with defined cognitive deficit (>or=1 s.d. below normal in the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS)), stable medication and disease state, were treated for 3 months with a weekly short (15 min) intravenous infusion of 40,000 IU rhEPO (N=20) or placebo (N=19). Main outcome measure was schizophrenia-relevant cognitive function at week 12. The neuropsychological test set (RBANS subtests delayed memory, language-semantic fluency, attention and Wisconsin Card Sorting Test (WCST-64) - perseverative errors) was applied over 2 days at baseline, 2 weeks, 4 weeks and 12 weeks of study participation. Both placebo and rhEPO patients improved in all evaluated categories. Patients receiving rhEPO showed a significant improvement over placebo patients in schizophrenia-related cognitive performance (RBANS subtests, WCST-64), but no effects on psychopathology or social functioning. Also, a significant decline in serum levels of S100B, a glial damage marker, occurred upon rhEPO. The fact that rhEPO is the first compound to exert a selective and lasting beneficial effect on cognition should encourage new treatment strategies for schizophrenia.

A neuroendocrinological hypothesis on gender effects of naltrexone in relapse prevention treatment

The ability of naltrexone to increase hypothalamo-pituitary-adrenocortical (HPA)-axis activity was recently reported to be associated with its effects on the reduction of craving for alcohol. We now present data showing naltrexone to be more efficacious in female alcoholics. Since HPA-axis might be interpreted as a key mechanism of action that could explain the observed gender differences in the abstinence maintenance treatment of alcohol addiction.

Long-term effects of pharmacotherapy on relapse prevention in alcohol dependence

BACKGROUND

There is growing evidence that pharmacological treatment with two of the best validated anticraving drugs, acamprosate and naltrexone, is efficacious in promoting abstinence in recently detoxified alcohol-dependent subjects.

OBJECTIVE

The stability of effects after termination of treatment remains to be answered, especially when combining both the drugs.

METHOD

After detoxification, 160 alcohol-dependent subjects participated in a randomized, double-blind, placebo-controlled trial. Patients received naltrexone or acamprosate or a combination of naltrexone and acamprosate or placebo for 12 weeks. Patients were assessed weekly by interview, self-report, questionnaires and laboratory screening. Additionally, follow-up evaluation based on telephone interview of participants, general practitioners and relatives was conducted 12 weeks after terminating the medication.

RESULTS

At week 12, the proportion of subjects relapsing to heavy drinking was significantly lower in the group with combined medication compared with both placebo and acamprosate (P < 0.05). No difference was detectable between acamprosate and naltrexone, both of which were superior to placebo (P < 0.05). Relapse rates were 28% (combined medication), 35% (naltrexone), 50% (acamprosate) and 75% (placebo). After follow-up (week 24), combined medication led to relapse rates significantly lower than placebo, but not lower than acamprosate. Again, both naltrexone and acamprosate were superior to placebo. Relapse rates were 80% (placebo), 54% (acamprosate), 53% (naltrexone) and 34% (combined medication).

CONCLUSIONS

The results of this study highlight the stability of effects of pharmacotherapy on relapse prevention in alcohol dependence.

Entwicklung und Evaluation eines Fortbildungsprogramms zur Partizipativen Entscheidungsfindung f�r die haus�rztliche Versorgung depressiver Patienten

Patient surveys show that many patients want broad information about their disease and treatment. Often they are interested to participate in the process of medical decision making, which could be realised with the concept of shared decision making where patient's values and needs are considered to the same extent as the treatment recommendations of evidence-based medicine. In depression care, it has been demonstrated so far that the active involvement of patients contributes to higher motivation for treatment. For enhancing patient's acceptance and motivation to avail themselves of medical treatment, a training program for general practitioners was developed and evaluated. It was the aim of the training to involve depressive patients in medical decision making. The training consists of depression-specific components (e. g. diagnosis, patient information, therapy) and general components (communication and shared decision making). The training was carried out in five sessions within a 6-month period (May to October 2003) embracing 20 h of training. Participants were 20 general practitioners in Southwest Germany. Physician's satisfaction with the training program is high. Especially in the fields of diagnosis and shared decision making the physicians clearly benefited. Transfer of shared decision making into daily routine was assessed as possible by the large majority of the trainees. Application of the training concept to other diseases and evaluation on the basis of daily routine is recommended. The training effects on medical care are presently being assessed in a randomised controlled trial.