Genome-wide interaction study of brain beta-amyloid burden and cognitive impairment in Alzheimer's disease.

The lack of strong association between brain beta-amyloid deposition and cognitive impairment has been a challenge for the Alzheimer's disease (AD) field. Although beta-amyloid is necessary for the pathologic diagnosis of AD, it is not sufficient to make the pathologic diagnosis or cause dementia. We sought to identify the genetic modifiers of the relation between cortical beta-amyloid burden (measured using [18F]Florbetapir-PET) and cognitive dysfunction (measured using ADAS-cog) by conducting a genome-wide interaction study on baseline data from participants in the Alzheimer's Disease Neuroimaging Initiative (ADNI) phases GO/2 (n=678). Near genome-wide significant interaction effect was observed for rs73069071 within the IAPP (amylin) and SLCO1A2 genes (P=6.2 × 10-8). Congruent results were found using data from participants followed up from ADNI-1 (Pone-tailed=0.028, n=165). Meta-analysis across ADNI-GO/2 and ADNI-1 revealed a genome-wide significant interaction effect (P=1.1 × 10-8). Our results were further supported by similar interaction effects on temporal lobe cortical thickness (whole-brain voxelwise analysis: familywise error corrected P=0.013) and longitudinal changes in ADAS-cog score and left middle temporal thickness and amygdalar volume (Pone-tailed=0.026, 0.019 and 0.003, respectively). Using postmortem beta-amyloid immunohistochemistry data from 243 AD participants in the Religious Orders Study and Memory and Aging Project, we also observed similar rs73069071-by-beta-amyloid deposition interaction effect on global cognitive function (Pone-tailed=0.005). Our findings provide insight into the complexity of the relationship between beta-amyloid burden and AD-related cognitive impairment. Although functional studies are required to elucidate the role of rs73069071 in AD pathophysiology, our results support the recently growing evidence on the role of amylin in AD.

In-vivo imaging of grey and white matter neuroinflammation in Alzheimer's disease: a positron emission tomography study with a novel radioligand, [18F]-FEPPA.

Our primary aim was to compare neuroinflammation in cognitively intact control subjects and patients with Alzheimer's disease (AD) by using positron emission tomography (PET) with translocator protein 18 kDa (TSPO)-specific radioligand [(18)F]-FEPPA. [(18)F]-FEPPA PET scans were acquired on a high-resolution research tomograph in 21 patients with AD (47- 81 years) and 21 control subjects (49-82 years). They were analyzed by using a 2-tissue compartment model with arterial plasma input function. Differences in neuroinflammation, indexed as [(18)F]-FEPPA binding were compared, adjusting for differences in binding affinity class as determined by a single polymorphism in the TSPO gene (rs6971). In grey matter areas, [(18)F]-FEPPA was significantly higher in AD compared with healthy control subjects. Large increases were seen in the hippocampus, prefrontal, temporal, parietal and occipital cortex (average Cohen's d= 0.89). Voxel-based analyses confirmed significant clusters of neuroinflammation in the frontal, temporal and parietal cortex in patients with AD. In white matter, [(18)F]-FEPPA binding was elevated in the posterior limb of the internal capsule, and the cingulum bundle. Higher neuroinflammation in the parietal cortex (r= -0.7, P= 0.005), and posterior limb of the internal capsule (r= -0.8, P=0.001) was associated with poorer visuospatial function. In addition, a higher [(18)F]-FEPPA binding in the posterior limb of the internal capsule was associated with a greater impairment in language ability (r= -0.7, P=0.004). Elevated neuroinflammation can be detected in AD patients throughout the brain grey and white matter by using [(18)F]-FEPPA PET. Our results also suggest that neuroinflammation is associated with some cognitive deficits.

The SORL1 gene and convergent neural risk for Alzheimer's disease across the human lifespan.

Prior to intervention trials in individuals genetically at-risk for late-onset Alzheimer's disease, critical first steps are identifying where (neuroanatomic effects), when (timepoint in the lifespan) and how (gene expression and neuropathology) Alzheimer's risk genes impact the brain. We hypothesized that variants in the sortilin-like receptor (SORL1) gene would affect multiple Alzheimer's phenotypes before the clinical onset of symptoms. Four independent samples were analyzed to determine effects of SORL1 genetic risk variants across the lifespan at multiple phenotypic levels: (1) microstructural integrity of white matter using diffusion tensor imaging in two healthy control samples (n=118, age 18-86; n=68, age 8-40); (2) gene expression using the Braincloud postmortem healthy control sample (n=269, age 0-92) and (3) Alzheimer's neuropathology (amyloid plaques and tau tangles) using a postmortem sample of healthy, mild cognitive impairment (MCI) and Alzheimer's individuals (n=710, age 66-108). SORL1 risk variants predicted lower white matter fractional anisotropy in an age-independent manner in fronto-temporal white matter tracts in both samples at 5% family-wise error-corrected thresholds. SORL1 risk variants also predicted decreased SORL1 mRNA expression, most prominently during childhood and adolescence, and significantly predicted increases in amyloid pathology in postmortem brain. Importantly, the effects of SORL1 variation on both white matter microstructure and gene expression were observed during neurodevelopmental phases of the human lifespan. Further, the neuropathological mechanism of risk appears to primarily involve amyloidogenic pathways. Interventions targeted toward the SORL1 amyloid risk pathway may be of greatest value during early phases of the lifespan.

Predicting Plasma Olanzapine Concentration Following a Change in Dosage: A Population Pharmacokinetic Study.

INTRODUCTION: Due to high inter-individual variability in peripheral pharmacokinetic parameters, dosing of antipsychotics currently relies on clinical trial-and-error, and predicting antipsychotic plasma concentrations before changing a dose has been a challenge. METHODS: Patients with schizophrenia receiving a stable dose of olanzapine were included. 2 plasma samples were collected at 2 given time points for the measurement of plasma olanzapine concentrations. At least 7 days after a dosage change of olanzapine, a third sample was collected. The plasma concentration of the third sample was predicted in a blinded fashion using a mixed-effects model with NONMEM(®), using the following information: the 2 baseline plasma concentrations, the interval between the last dose and blood draw, and clinical and demographic information. RESULTS: 31 subjects (mean±SD age=56.0±11.6; 19 men) were enrolled. The mean prediction (95% confidence interval) errors were 1.6 (-2.8 to 6.0) ng/mL. A highly significant correlation was observed between the observed and predicted concentrations of the third sample (r=0.91, p<0.001). DISCUSSION: Plasma olanzapine concentrations following an actual dosage change can be predicted in advance with a high degree of certainty.

Effect of dorsolateral prefrontal cortex structural measures on neuroplasticity and response to paired-associative stimulation in Alzheimer's dementia.

Long-term potentiation (LTP)-like activity can be induced by stimulation protocols such as paired associative stimulation (PAS). We aimed to determine whether PAS-induced LTP-like activity (PAS-LTP) of the dorsolateral prefrontal cortex (DLPFC) is associated with cortical thickness and other structural measures impaired in Alzheimer's dementia (AD). We also explored longitudinal relationships between these brain structures and PAS-LTP response after a repetitive PAS (rPAS) intervention. Mediation and regression analyses were conducted using data from randomized controlled trials with AD and healthy control participants. PAS-electroencephalography assessed DLPFC PAS-LTP. DLPFC thickness and surface area were acquired from T1-weighted magnetic resonance imaging. Fractional anisotropy and mean diffusivity (MD) of the superior longitudinal fasciculus (SLF)-a tract important to induce PAS-LTP-were measured with diffusion-weighted imaging. AD participants exhibited reduced DLPFC thickness and increased SLF MD. There was also some evidence that reduction in DLPFC thickness mediates DLPFC PAS-LTP impairment. Longitudinal analyses showed preliminary evidence that SLF MD, and to a lesser extent DLPFC thickness, is associated with DLPFC PAS-LTP response to active rPAS. This study expands our understanding of the relationships between brain structural changes and neuroplasticity. It provides promising evidence for a structural predictor to improving neuroplasticity in AD with neurostimulation. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.

Genetic variation in CYP3A43 explains racial difference in olanzapine clearance.

The antipsychotic drug, olanzapine, one of the most widely used drugs in clinical medicine, has a high rate of discontinuation due to inefficacy and/or adverse effects. We identified a single nucleotide polymorphism in the drug metabolizing enzyme, cytochrome P450 3A43 (CYP3A43; rs472660), that highly significantly predicted olanzapine clearance in the Clinical Antipsychotic Trials of Intervention Effectiveness trial (P=5.9e(-7)). Moreover, at standard antipsychotic doses, 50% of individuals with the high clearance genotype (AA) have trough blood levels below the therapeutic range. Interestingly, a much higher proportion of African Americans carry the A allele compared with Caucasians (allele frequency 67 vs 14%). After accounting for CYP3A43 genotype, race is no longer a significant predictor of olanzapine clearance. Olanzapine clearance was associated with measures of clinical response. Patients with greater clearance had higher symptom ratings and were more likely to discontinue treatment due to an inadequate response. Our data identify a genetic mechanism for variation in olanzapine response and demonstrate that blood level monitoring of olanzapine treatment is advisable.

Regression models in clinical studies: determining relationships between predictors and response.

Multiple regression models are increasingly being applied to clinical studies. Such models are powerful analytic tools that yield valid statistical inferences and make reliable predictions if various assumptions are satisfied. Two types of assumptions made by regression models concern the distribution of the response variable and the nature or shape of the relationship between the predictors and the response. This paper addresses the latter assumption by applying a direct and flexible approach, cubic spline functions, to two widely used models: the logistic regression model for binary responses and the Cox proportional hazards regression model for survival time data.

Acute antidepressant effect following pulse loading with intravenous and oral clomipramine.

A double-blind, randomized trial of oral vs intravenous clomipramine hydrochloride pulse-loading dosing regimens was conducted. After a two-week drug-free assessment period, 22 inpatients with a diagnosis of major depressive disorder were given either an evening infusion of 150 mg of clomipramine hydrochloride and placebo tablets or 150 mg of oral clomipramine hydrochloride and an isotonic saline infusion. Twenty-four hours later, this procedure was repeated using a dose of 200 mg of clomipramine hydrochloride. Patients received no further medication over the next five days. The mean Hamilton Depression Rating Scale score for all patients, five days after pulse loading, had dropped by 35% (range, 13.3% to -82.4%). This improvement was significant, as was the amelioration in the Raskin Severity for Depression Scale and the Beck Depression Inventory scores. Although the bioavailability of parenteral clomipramine was greater, there were no significant differences in either efficacy or side effects between the two groups. Pronounced early improvements in severe depressive symptoms may be achieved via loading dose regimens with clomipramine in the absence of continuous treatment.

Elevated platelet factor 4 and beta-thromboglobulin plasma levels in depressed patients with ischemic heart disease.

Clinical depression has recently been recognized as an independent risk factor for cardiac mortality in patients after myocardial infarction. The underlying mechanisms of this increased mortality remain unclear. This study investigated the hypothesis that patients suffering from ischemic heart disease (IHD) and depression concurrently may have abnormal platelet activation resulting in an increased risk of thrombosis. Platelet factor 4 (PF4) and beta-thromboglobulin (beta-TG) were measured in young healthy control subjects, in nondepressed patients with IHD, and in depressed patients with IHD. Mean PF4 and beta-TG plasma levels in the IHD group with depression were found to be significantly higher than those of the control and IHD groups. This increase was not related to age, gender, racial difference, aspirin use, or severity of cardiac disease. This finding suggests that in depressed patients with IHD there is greater platelet activation, and may indicate an increased risk of thrombotic complications.

Fluvoxamine versus desipramine: comparative polysomnographic effects.

Electroencephalogram sleep measures over a 4-week period were obtained on 35 inpatients with major depression (unipolar) who received either fluvoxamine or desipramine in a randomized double-blind trial. Fluvoxamine showed immediate rapid eye movement (REM) sleep suppression and an alerting effect on sleep continuity measures. In contrast, desipramine administration was associated with REM suppression and sleep continuity improvement. The "alerting" quality of fluvoxamine, similar to other serotonergic antidepressants, appears to be unrelated to a lack of clinical efficacy, but may be related to persistent REM sleep suppression. However, it is premature to comment on the serotonin specificity for REM sleep.

Association of plasma homovanillic acid with behavioral symptoms in patients diagnosed with dementia: a preliminary report.

Neuroleptic treatment of psychotic symptoms or agitated behavior in elderly patients diagnosed with dementia is associated with reduced efficacy and increased rates of neuroleptic-induced parkinsonism in comparison to younger patients with schizophrenia. We report the first study to examine the relationship between an in vivo measure of dopaminergic function, plasma homovanillic acid (pHVA), and ratings of psychosis, agitation, and parkinsonism before and after neuroleptic treatment in dementia patients. Pretreatment pHVA was significantly correlated with parkinsonian rigidity, with a trend observed with agitation and hostility. Though mean pHVA did not change during perphenazine treatment, intraindividual change in pHVA at day 15 was correlated with improvement in hostility, with a similar trend for improvement in agitation. These preliminary findings are consistent with reports associating dopaminergic function with agitated, but not psychotic, symptoms in patients diagnosed with dementia, and with a reduced responsivity of dopaminergic systems to neuroleptic treatment in these patients.

Endogenous concentrations of DHEA and DHEA-S decrease with remission of depression in older adults.

BACKGROUND: Clinical studies of endogenous concentrations of dehydroepiandrosterone (DHEA) and its sulfated conjugate DHEA-S in depression are limited. This study was designed to evaluate the influence of successful pharmacological treatment of late-life depression on concentrations of DHEA, DHEA-S and cortisol. METHODS: We determined endogenous concentrations of DHEA, DHEA-S and cortisol in elderly control subjects (n = 16) and in elderly depressed patients who remitted (n = 44) or failed to remit (n = 16) with pharmacological treatment. Depressed patients were treated for 12 weeks with either nortriptyline or paroxetine. RESULTS: In remitters, DHEA and DHEA-S concentrations were lower at week 12 than at week 0 (p =.002 and p =.0001, respectively). In the nonremitters and control subjects, neither DHEA nor DHEA-S concentrations changed. Decreases in hormone concentrations were associated with improvement in mood and functioning in depressed patients. Although cortisol concentrations decreased in remitters and nonremitters, the change was not significant. CONCLUSIONS: Our data suggest that the decrease in DHEA and DHEA-S in remitters is related to remission of depression rather than to a direct drug effect on steroids, as nonremitters had no change in hormone concentrations.

Treatment of nortriptyline's side effects in elderly patients: a double-blind study of bethanechol.

A double-blind, placebo-controlled study of bethanechol was conducted in 26 elderly depressed patients being treated with nortriptyline. Patients receiving bethanechol had reduced subjective complaints of anticholinergic side effects and showed a trend toward improvement on an objective measure of salivary flow. The potential use of bethanechol in older patients to reduce morbidity and improve compliance with medication regimens is discussed.

Newer antidepressants and the cytochrome P450 system.

OBJECTIVE: This review evaluates the in vitro and in vivo evidence for inhibition of cytochrome P450 enzymes by the newer antidepressants and provides clinical recommendations for avoiding and managing drug interactions. METHOD: The international literature on the cytochrome P450 system and related drug interactions from 1966 to 1995 was reviewed. In vitro studies, pharmacokinetic trials in human subjects, and case reports were assessed. RESULTS: The newer antidepressants each inhibit a different cluster of cytochrome P450 enzymes, which are of relevance to the potential for drug interactions. Cytochrome P450 1A2 is inhibited by fluvoxamine and is implicated in drug interactions with theophylline, clozapine, and others. Fluoxetine, norfluoxetine, sertraline, and paroxetine are potent in vitro inhibitors of cytochrome P450 2D6 and are capable of causing marked elevations in plasma desipramine and nortriptyline concentrations. Fluoxetine, sertraline, and fluvoxamine are believed to inhibit cytochrome P450 2C because of observed interactions with phenytoin, diazepam, and other drugs metabolized by these enzymes. Cytochrome P450 3A4 metabolizes terfenadine, astemizole, carbamazepine, alprazolam, triazolam, and other benzodiazepines. Plasma concentrations of these drugs have increased when they are administered with fluvoxamine, nefazodone, fluoxetine, and sertraline. CONCLUSIONS: The majority of the newer antidepressants are associated with a risk for clinically significant drug interactions. A rapidly growing body of literature provides evidence for a distinct profile of cytochrome P450 inhibition and drug interaction risks by individual antidepressants. These findings underscore the need for definitive in vivo interaction studies of plasma from phenotyped patients treated with clinically effective antidepressant doses of medication, for direct comparative clinical studies, and for studies assessing the utility of phenotyping in clinical practice.

Comorbid anxiety disorders in depressed elderly patients.

OBJECTIVE: Anxiety disorders are common in adults with depressive disorders, but several studies have suggested a relatively low prevalence of anxiety disorders in older individuals with depression. This cross-sectional study measured current and lifetime rates and associated clinical features of anxiety disorders in depressed elderly patients. METHOD: History of anxiety disorders was assessed by using a structured diagnostic instrument in 182 depressed subjects aged 60 and older seen in primary care and psychiatric settings. Associations between comorbid anxiety disorders and baseline characteristics were measured. The modified structured instrument allowed detection of symptoms that met inclusion criteria for generalized anxiety disorder in a depressive episode. RESULTS: Thirty-five percent of older subjects with depressive disorders had at least one lifetime anxiety disorder diagnosis, and 23% had a current diagnosis. The most common current comorbid anxiety disorders were panic disorder (9.3%), specific phobias (8.8%), and social phobia (6.6%). Symptoms that met inclusion criteria for generalized anxiety disorder, measured separately, were present in 27.5% of depressed subjects. Presence of a comorbid anxiety disorder was associated with poorer social function and a higher level of somatic symptoms. Symptoms of generalized anxiety disorder were associated with a higher level of suicidality. CONCLUSIONS: Contrary to previous reports, the present study found a relatively high rate of current and lifetime anxiety disorders in elderly depressed individuals. Comorbid anxiety disorders and symptoms of generalized anxiety disorder were associated with a more severe presentation of depressive illness in elderly subjects.

Influence of serotonin-transporter-linked promoter region polymorphism on platelet activation in geriatric depression.

OBJECTIVE: Depression has been associated with increased platelet activation. Variations in the serotonin-transporter-linked promoter region (5-HTTLPR) polymorphism may influence the degree of activation. The authors examined the association among depression, platelet activation, and 5-HTTLPR genotype. METHOD: Elderly subjects with (N=61) and without (N=12) major depression were assessed for cognitive impairment, cardiovascular disease, and two indices of platelet activation. The depressed subjects were genotyped for the 5-HTTLPR polymorphism. RESULTS: The depressed subjects were older, were more cognitively impaired, and had higher platelet factor 4 and beta-thromboglobulin levels; cardiovascular disease was minimal in both groups. In the depressed group, subjects with the 5-HTTLPR l/l genotype had significantly higher platelet factor 4 and beta-thromboglobulin levels. CONCLUSIONS: Platelet activation is increased in elderly depressed patients, especially those with the 5-HTTLPR l/l genotype. This finding suggests how genetic differences may influence cardiovascular mortality in depressed patients with ischemic heart disease.

Serum anticholinergicity in elderly depressed patients treated with paroxetine or nortriptyline.

OBJECTIVE: The authors' goal was to compare serum anticholinergicity of 61 elderly depressed patients randomly assigned to double-blind treatment with paroxetine (N=31) or nortriptyline (N=30). METHOD: Both antidepressants were titrated in a standardized manner, and plasma was sampled weekly for measurement of paroxetine and nortriptyline and its hydroxy metabolite concentrations. Serum anticholinergicity was measured at baseline and after 1, 4, and 6 weeks of treatment. Side effects were assessed by using a validated scale. RESULTS: After correcting for pretreatment anticholinergicity, the authors found that mean serum anticholinergicity for the nortriptyline-treated patients was significantly greater than that for the paroxetine group at all weeks assessed. Serum anticholinergicity was significantly correlated with nortriptyline but not with paroxetine plasma levels. Complaints of dry mouth and tachycardia were significantly more frequent and severe in the nortriptyline group. CONCLUSIONS: These findings suggest that, at therapeutic plasma concentrations, paroxetine has approximately one-fifth the anticholinergic potential of nortriptyline in older patients.

Changes in cognitive functioning following treatment of late-life depression.

OBJECTIVE: Knowledge of the relationship between various clinical characteristics and cognitive functioning is advancing, but little is known about the cognitive response to treatment for geriatric depression. The purpose of this study was to examine the cognitive response to treatment for patients with late-life depression. METHOD: Subjects included 45 nondemented, elderly depressed patients who achieved remission after 12 weeks of antidepressant treatment and 20 elderly comparison subjects. All subjects were administered a battery of clinical measures, including cognitive screening instruments, before and after treatment. RESULTS: As a group, the elderly depressed patients showed a small improvement in overall cognitive functioning after treatment. Among depressed patients with concomitant cognitive impairment at baseline, performance on the Mattis Dementia Rating Scale domains of conceptualization and initiation/perseveration improved significantly relative to those of depressed patients with normal cognition. Despite the improvement following treatment, the overall level of cognitive functioning in the elderly depressed patients with cognitive impairment at baseline remained mildly impaired, especially in the memory and initiation/perseveration domains. CONCLUSIONS: Elderly depressed patients with cognitive impairment may experience improvement in specific domains following antidepressant treatment but may not necessarily reach normal levels of performance, particularly in memory and executive functions. This subgroup of late-life depression patients is likely at high risk of developing progressive dementia.

Treatment of consecutive episodes of major depression in the elderly.

OBJECTIVE: The purpose of this study was to determine treatment outcome in elderly patients with consecutively treated episodes of recurrent unipolar major depression. METHOD: Subjects were 32 "young" elderly patients with recurrent unipolar depression (mean age = 66.8 years, SD = 5.1) and with two consecutively treated episodes of major depression. Both index and subsequent episodes of major depression were treated in open trial with combined nortriptyline and interpersonal psychotherapy. Rates of remission in index and subsequent episodes were compared by using nonparametric statistics and survival analysis with proportional hazards modeling. RESULTS: Of 30 patients who completed treatment of the subsequent episode, 27 (90%) achieved stable remission of symptoms in both consecutively treated episodes, whereas three patients (10%) did not. Twenty-two (81%) of 27 patients who responded to treatment had a shorter time to remission in treatment of the subsequent episode than in the index episode. Survival analysis with proportional hazards modeling detected a significant difference in time to remission of the index and subsequent episodes (32 paired observations). CONCLUSIONS: In this research study group, recurrent episodes of unipolar major depression in the young elderly were successfully treated to remission in over 80% of patients by using combined pharmacotherapy and psychotherapy similar to that employed in treatment of the index episode. Remission rate and time to remission in consecutively treated episodes were comparable to those in a group of midlife patients with recurrent depression reported by Kupfer et al. in 1989. Thus, recurrent depressive disorder appears to be as treatable in the young elderly as it is in midlife patients.

Three-year outcomes of maintenance nortriptyline treatment in late-life depression: a study of two fixed plasma levels.

OBJECTIVE: This study compared the long-term efficacy of two fixed plasma levels of nortriptyline in preventing or delaying recurrence of major depression in elderly patients and in minimizing residual depressive symptoms and somatic complaints. METHOD: The authors randomly assigned 41 elderly patients with histories of recurrent major depression to 3-year, double-blind maintenance pharmacotherapy using nortriptyline, with controlled plasma concentrations of 80-120 ng/ml versus 40-60 ng/ml. The authors compared times to, and rates of, recurrence of major depression. They also compared frequencies of side effects, noncompliance episodes, and subsyndromal symptomatic flare-ups. RESULTS: Major depressive episodes recurred for six (29%) of 21 subjects in the 80-120-ng/ml condition and eight (40%) of 20 subjects in the 40-60-ng/ml condition, a nonsignificant difference. Most recurrences took place in the first year of maintenance treatment. Hamilton depression scores in the subsyndromal range (higher than either 10 or 7) occurred significantly more often at 40-60 ng/ml, while constipation occurred significantly more often at 80-120 ng/ml. The proportions of patients reporting missed doses did not differ. CONCLUSIONS: Maintenance pharmacotherapy with nortriptyline at 80-120 ng/ml is associated with fewer residual depressive symptoms, that is, a less variable long-term response, than pharmacotherapy at 40-60 ng/ml, but constipation is more frequent and there is no difference in recurrence of syndromal major depressive episodes. Treatment at 80-120 ng/ml may be preferable, because of fewer residual symptoms and less variability of response, as long as side effect burden can be managed successfully.