Alzheimer Disease: McLaughlin T

Nikolaev A, McLaughlin T, O'Leary DD, Tessier-Lavigne M. · Division of Research, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, USA. · Nature. · Pubmed #19225519 No free full text.

Abstract: Naturally occurring axonal pruning and neuronal cell death help to sculpt neuronal connections during development, but their mechanistic basis remains poorly understood. Here we report that beta-amyloid precursor protein (APP) and death receptor 6 (DR6, also known as TNFRSF21) activate a widespread caspase-dependent self-destruction program. DR6 is broadly expressed by developing neurons, and is required for normal cell body death and axonal pruning both in vivo and after trophic-factor deprivation in vitro. Unlike neuronal cell body apoptosis, which requires caspase 3, we show that axonal degeneration requires caspase 6, which is activated in a punctate pattern that parallels the pattern of axonal fragmentation. DR6 is activated locally by an inactive surface ligand(s) that is released in an active form after trophic-factor deprivation, and we identify APP as a DR6 ligand. Trophic-factor deprivation triggers the shedding of surface APP in a beta-secretase (BACE)-dependent manner. Loss- and gain-of-function studies support a model in which a cleaved amino-terminal fragment of APP (N-APP) binds DR6 and triggers degeneration. Genetic support is provided by a common neuromuscular junction phenotype in mutant mice. Our results indicate that APP and DR6 are components of a neuronal self-destruction pathway, and suggest that an extracellular fragment of APP, acting via DR6 and caspase 6, contributes to Alzheimer's disease.

Zhu CW, Leibman C, McLaughlin T, Zbrozek AS, Scarmeas N, Albert M, Brandt J, Blacker D, Sano M, Stern Y. · Geriatric Research, Education, and Clinical Center (GRECC), James J. Peters VA Medical Center, Bronx, NY, NY 10468, USA. · Dement Geriatr Cogn Disord. · Pubmed #18946219 links to  free full text

Abstract: BACKGROUND/AIMS: To examine the incremental effect of patients' dependence on others, on cost of medical and nonmedical care, and on informal caregiving hours over time. METHODS: Data are obtained from 172 patients from the Predictors Study, a large, multicenter cohort of patients with probable Alzheimer disease (AD) followed annually for 4 years in 3 University-based AD centers in the USA. Enrollment required a modified Mini-Mental State Examination score >or=30. We examined the effects of patient dependence (measured by the Dependence Scale, DS) and function (measured by the Blessed Dementia Rating Scale, BDRS) on medical care cost, nonmedical care cost, and informal caregiving time using random effects regression models. RESULTS: A one-point increase in DS score was associated with a 5.7% increase in medical cost, a 10.5% increase in nonmedical cost, and a 4.1% increase in caregiving time. A one-point increase in BDRS score was associated with a 7.6% increase in medical cost, a 3.9% increase in nonmedical cost and an 8.7% increase in caregiving time. CONCLUSIONS: Both functional impairment and patient dependence were associated with higher costs of care and caregiving time. Measures of functional impairment and patient dependence provide unique and incremental information on the overall impact of AD on patients and their caregivers.

Zhu CW, Leibman C, McLaughlin T, Scarmeas N, Albert M, Brandt J, Blacker D, Sano M, Stern Y. · Geriatric Research, Education, and Clinical Center, Program of Research on Serious Physical and Mental Illness, James J Peters Veterans Affairs Medical Center, Bronx, New York 10468, USA. · J Am Geriatr Soc. · Pubmed #18662215 links to  free full text

Abstract: OBJECTIVES: To estimate incremental effects of patients' dependence and function on costs of care during the early stages of Alzheimer's disease (AD) and to compare strengths of their relationships with different cost components. DESIGN: Multicenter, cross-sectional, observational study. SETTING: Three university hospitals in the United States. PARTICIPANTS: One hundred seventy-nine community-living patients with probable AD, with modified Mini-Mental State Examination scores of 30 or higher. MEASUREMENTS: Patients' dependence was measured using the Dependence Scale (DS). Functional capacity was measured using the Blessed Dementia Rating Scale (BDRS). Total cost was measured by summing direct medical costs and informal costs. Direct medical costs included costs of hospitalization, outpatient treatment and procedures, assistive devices, and medications. Informal costs were estimated from time spent helping with basic and instrumental activities of daily living for up to three caregivers per patient using national average hourly earnings as wage rate. RESULTS: DS and BDRS were associated with higher total cost; a 1-point increase in DS was associated with a $1,832 increase in total cost, and a 1-point increase in BDRS was associated with a $3,333 increase. Examining component costs separately identified potential differences between DS and BDRS. A 1-point increase in BDRS was associated with a $1,406 increase in direct medical cost. A 1-point increase in DS was associated with a $1,690 increase in informal cost. CONCLUSION: Patients' dependence and function related differently to direct medical and informal cost, suggesting that measures of function and dependence provided unique information for explaining variations in cost of care for patients with AD, highlighting the value in measuring both constructs.