Plasma Leptin and Alzheimer Protein Pathologies Among Older Adults

Importance

Many epidemiologic studies have suggested that low levels of plasma leptin, a major adipokine, are associated with increased risk of Alzheimer disease (AD) dementia and cognitive decline. Nevertheless, the mechanistic pathway linking plasma leptin and AD-related cognitive decline is not yet fully understood.

Objective

To examine the association of plasma leptin levels with in vivo AD pathologies, including amyloid-beta (Aβ) and tau deposition, through both cross-sectional and longitudinal approaches among cognitively unimpaired older adults.

Design, Setting, and Participants

This was a longitudinal cohort study from the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer Disease. Data were collected from January 1, 2014, to December 31, 2020, and data were analyzed from July 11 to September 6, 2022. The study included a total of 208 cognitively unimpaired participants who underwent baseline positron emission tomography (PET) scans for brain Aβ deposition. For longitudinal analyses, 192 participants who completed both baseline and 2-year follow-up PET scans for brain Aβ deposition were included.

Exposure

Plasma leptin levels as assessed by enzyme-linked immunosorbent assay.

Main Outcomes and Measures

Baseline levels and longitudinal changes of global Aβ and AD-signature region tau deposition measured by PET scans.

Results

Among the 208 participants, the mean (SD) age was 66.0 (11.3) years, 114 were women (54.8%), and 37 were apolipoprotein E ε4 carriers (17.8%). Lower plasma leptin levels had a significant cross-sectional association with greater brain Aβ deposition (β = -0.04; 95% CI, -0.09 to 0.00; P = .046), while there was no significant association between plasma leptin levels and tau deposition (β = -0.02; 95% CI, -0.05 to 0.02; P = .41). In contrast, longitudinal analyses revealed that there was a significant association between lower baseline leptin levels and greater increase of tau deposition over 2 years (β = -0.06; 95% CI, -0.11 to -0.01; P = .03), whereas plasma leptin levels did not have a significant association with longitudinal change of Aβ deposition (β = 0.006; 95% CI, 0.00-0.02; P = .27).

Conclusions and Relevance

The present findings suggest that plasma leptin may be protective for the development or progression of AD pathology, including both Aβ and tau deposition.

Association between brain amyloid deposition and longitudinal changes of white matter hyperintensities

BACKGROUND

Growing evidence suggests that not only cerebrovascular disease but also Alzheimer's disease (AD) pathological process itself cause cerebral white matter degeneration, resulting in white matter hyperintensities (WMHs). Some preclinical evidence also indicates that white matter degeneration may precede or affect the development of AD pathology. This study aimed to clarify the direction of influence between in vivo AD pathologies, particularly beta-amyloid (Aβ) and tau deposition, and WMHs through longitudinal approach.

METHODS

Total 282 older adults including cognitively normal and cognitively impaired individuals were recruited from the Korean Brain Aging Study for the Early Diagnosis and Prediction of Alzheimer's Disease (KBASE) cohort. The participants underwent comprehensive clinical and neuropsychological assessment, [11C] Pittsburgh Compound B PET for measuring Aβ deposition, [18F] AV-1451 PET for measuring tau deposition, and MRI scans with fluid-attenuated inversion recovery image for measuring WMH volume. The relationships between Aβ or tau deposition and WMH volume were examined using multiple linear regression analysis. In this analysis, baseline Aβ or tau were used as independent variables, and change of WMH volume over 2 years was used as dependent variable to examine the effect of AD pathology on increase of WMH volume. Additionally, we set baseline WMH volume as independent variable and longitudinal change of Aβ or tau deposition for 2 years as dependent variables to investigate whether WMH volume could precede AD pathologies.

RESULTS

Baseline Aβ deposition, but not tau deposition, had significant positive association with longitudinal change of WMH volume over 2 years. Baseline WMH volume was not related with any of longitudinal change of Aβ or tau deposition for 2 years. We also found a significant interaction effect between baseline Aβ deposition and sex on longitudinal change of WMH volume. Subsequent subgroup analyses showed that high baseline Aβ deposition was associated with increase of WMH volume over 2 years in female, but not in male.

CONCLUSIONS

Our findings suggest that Aβ deposition accelerates cerebral WMHs, particularly in female, whereas white matter degeneration appears not influence on longitudinal Aβ increase. The results also did not support any direction of influence between tau deposition and WMHs.

[Pelvic vein thrombosis : Current treatment options and importance of recanalization procedures]

Venous thrombosis is a frequent disorder. A distinction is made between an acute phase of the disease and a chronic manifestation, the postthrombotic syndrome. In particular, proximal venous thrombosis/pelvic vein thrombosis can cause a life-threatening pulmonary embolism during the acute phase of the disease. The postthrombotic syndrome is characterized by the remodeling of the affected venous section, which is often caused by inflammation. Locally, the typical clinical finding is caused by scarred stricture of the vein with restricted drainage and peripheral venous hypertension. Acute thrombosis should be primarily treated by therapeutic anticoagulation and compression therapy of the affected extremity. The duration of these measures depends on clinical presentation, cause (provoked, unprovoked) and risk factors for venous thrombosis/recurrent thrombosis. Venous revascularization procedures are important both in the acute phase of the disease and in the treatment of postthrombotic syndrome. The recanalization treatment is mostly carried out as an endovascular or hybrid intervention and venous bypass procedures are reserved for special situations.

Targeting GD2 after allogeneic SCT: effector cell composition defines the optimal use of ch14.18 and the bispecific antibody construct NG-CU (GD2-CD3)

We investigated whether T cell-recruiting bispecific anti-CD3/GD2 antibody NG-CU might be an alternative to therapeutic anti-GD2 monoclonal antibody (mAb) ch14.18, mediating complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC) through natural killer (NK) cells for immunotherapy in high-risk/relapsed neuroblastoma after autologous/allogeneic stem cell transplantation (auto/alloSCT). Different antibody concentrations and effector-to-target ratios (E:T) were evaluated using xCELLigence RTCA system, peripheral blood mononuclear cells (PBMCs) (healthy donors and patients after alloSCT), and neuroblastoma cell lines (LS/LAN-1). Mean specific lysis of LS cells utilizing PBMCs from healthy donors and ch14.18 (1 µg/ml) was 40/66/75% after 12/24/48 h compared to 66/93/100% in the presence of NG-CU (100 ng/ml). NG-CU showed enhanced cytotoxicity compared to ch14.18, even at lower concentrations and E:T ratios, and completely eradicated LS cells after 72 h. To decipher the influence of effector cell subsets on lysis, different ratios of T and NK cells were tested. At a ratio of 1:1, ch14.18 was more effective than NG-CU. Using patient PBMCs taken at different time points posttransplant, significant lysis with both constructs was detectable depending on percentages and total numbers of T and NK cells; in the early posttransplant phase, NK cells were predominant and ch14.18 was superior, whereas later on, T cells represented the majority of immune cells and NG-CU was more effective. Our study highlights the importance of analyzing effector cell subsets in patients before initiating antibody-based therapy. Consequently, we propose an adjusted administration of both antibody constructs, considering the state of posttransplant immune recovery, to optimize anti-tumor activity.

Body mass index and two-year change of in vivo Alzheimer's disease pathologies in cognitively normal older adults

BACKGROUND

Low body mass index (BMI) or underweight status in late life is associated with an increased risk of dementia or Alzheimer's disease (AD). However, the relationship between late-life BMI and prospective longitudinal changes of in-vivo AD pathology has not been investigated.

METHODS

This prospective longitudinal study was conducted as part of the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer's Disease (KBASE). A total of 194 cognitive normal older adults were included in the analysis. BMI at baseline was measured, and two-year changes in brain Aβ and tau deposition on PET imaging were used as the main outcomes. Linear mixed-effects (LME) models were used to examine the relationships between late-life BMI and longitudinal change in AD neuropathological biomarkers.

RESULTS

A lower BMI at baseline was significantly associated with a greater increase in tau deposition in AD-signature region over 2 years (β, -0.018; 95% CI, -0.028 to -0.004; p = .008), In contrast, BMI was not related to two-year changes in global Aβ deposition (β, 0.0002; 95% CI, -0.003 to 0.002, p = .671). An additional exploratory analysis for each sex showed lower baseline BMI was associated with greater increases in tau deposition in males (β, -0.027; 95% CI, -0.046 to -0.009; p = 0.007), but not in females.

DISCUSSION

The findings suggest that lower BMI in late-life may predict or contribute to the progression of tau pathology over the subsequent years in cognitively unimpaired older adults.

Sex differences in the progression of glucose metabolism dysfunction in Alzheimer's disease

Alzheimer's disease (AD) is a common neurodegenerative disease characterized by amyloid plaques and impaired brain metabolism. Because women have a higher prevalence of AD than men, sex differences are of great interest. Using cross-sectional and longitudinal data, we showed sex-dependent metabolic dysregulations in the brains of AD patients. Cohort 1 (South Korean, n = 181) underwent Pittsburgh compound B-PET, fluorodeoxyglucose-PET, magnetic resonance imaging, and blood biomarker (plasma tau and beta-amyloid 42 and 40) measurements at baseline and two-year follow-ups. Transcriptome analysis of data from Cohorts 2 and 3 (European, n = 78; Singaporean, n = 18) revealed sex differences in AD-related alterations in brain metabolism. In women (but not in men), all imaging indicators displayed consistent correlation curves with AD progression. At the two-year follow-up, clear brain metabolic impairment was revealed only in women, and the plasma beta-amyloid 42/40 ratio was a possible biomarker for brain metabolism in women. Furthermore, our transcriptome analysis revealed sex differences in transcriptomes and metabolism in the brains of AD patients as well as a molecular network of 25 female-specific glucose metabolic genes (FGGs). We discovered four key-attractor FGG genes (ALDOA, ENO2, PRKACB, and PPP2R5D) that were associated with amyloid/tau-related genes (APP, MAPT, BACE1, and BACE2). Furthermore, these genes successfully distinguished amyloid positivity in women. Understanding sex differences in the pathogenesis of AD and considering these differences will improve development of effective diagnostics and therapeutic treatments for AD.

Low Ankle-Brachial Index Relates to Alzheimer-Signature Cerebral Glucose Metabolism in Cognitively Impaired Older Adults

BACKGROUND

Ankle-brachial index (ABI), an indicator of atherosclerosis or arterial stiffness, has been associated with Alzheimer's disease (AD) dementia and related cognitive impairment. Nevertheless, only limited information is available regarding its contribution to brain alterations leading to cognitive decline in late-life.

OBJECTIVE

We aimed to investigate the relationship of ABI with in vivo AD pathologies and cerebrovascular injury in cognitively impaired older adults.

METHODS

Total 127 cognitively impaired (70 mild cognitive impairment and 57 AD dementia) individuals, who participated in an ongoing prospective cohort study, were included. All participants underwent comprehensive clinical and neuropsychological assessment, ABI measurement, apolipoprotein E (APOE) ɛ4 genotyping, and multi-modal brain imaging including [11C] Pittsburgh Compound B (PiB)-positron emission tomography (PET) and [18F] fludeoxyglucose (FDG)-PET, and MRI.

RESULTS

General linear model analysis showed significant relationship between ABI strata (low ABI: <1.00, normal ABI: 1.00-1.29, and high ABI: ≥1.30) and AD-signature region cerebral glucose metabolism (AD-CM), even after controlling age, sex, clinical dementia rating-sum of box, and APOE ɛ4 positivity (p = 0.029). Post hoc comparison revealed that low ABI had significantly lower AD-CM than middle and high ABI, while no difference of AD-CM was found between middle and high ABI. There was no significant difference of global Aβ deposition, AD-signature region cortical thickness, and white matter hyperintensity volume between the three ABI strata.

CONCLUSION

Our findings suggest that lower ABI, likely related to atherosclerosis, may contribute to the aggravation of AD-related regional neurodegeneration in cognitively impaired older adults.

Development of a Cognitive Composite for Preclinical Alzheimer's Disease in Korean Older Adults

BACKGROUND

As tracking subtle cognitive declines in the preclinical stage of Alzheimer's disease (AD) is difficult with traditional individual outcome measures, need for cognitive composite for preclinical AD is widely recognized.

OBJECTIVE

We aimed to develop culturally appropriate cognitive composite that sensitively identifies subtle cognitive decline of preclinical AD in Korean older adults.

METHODS

A total 225 cognitively normal elderly individuals from the Korean Brain Aging Study for the Early Diagnosis and Prediction of Alzheimer's Disease, were included. Tests of episodic memory, orientation, and executive function were carefully selected through review of previously established composites. Three candidate composites including Consortium to Establish a Registry for Alzheimer's Disease Word list recall (WLR), Logical memory (LM) II, and Mini-Mental status examination (MMSE) in common, and Letter fluency test (LF), category fluency test, or Stroop color and word test, were selected.

RESULTS

Student t-tests demonstrated that only the composite composed of WLR, LM II, MMSE, and LF (Composite 1) showed a significant difference in score decline over two-year follow-up period between Aβ positive and negative group (p = 0.03). Linear mixed model analyses also showed that the Aβ x time interaction effect was significant only for Composite 1 (p = 0.025). Based on the results, Composite 1 was chosen as the final cognitive composite for preclinical Alzheimer's disease (CPAD).

CONCLUSIONS

CPAD can be used to assess subtle cognitive decline of preclinical AD in clinical research settings, especially in Korean older adults. It also may be used for monitoring progression or treatment benefits in clinical practices.

The Effects of Depression and Fear in Dual-Income Parents on Work-Family Conflict During the COVID-19 Pandemic

This study investigated depression and fear in dual-income parents during the COVID-19 pandemic as predictors of work-family conflict. Using a cross-sectional design, we recruited 214 dual-income parents aged 20 years or older with preschool and primary school children in Korea. Data were collected via an online survey. In the final model for hierarchical regression analysis, the strongest predictor of work-family conflict was depression (β = .43, p < .001), followed by fear (β = .23, p < .001), then weekly working hours (β = .12, p < .05). The final model was statistically significant (F = 29.80, p < .001), with an explanatory power of 35%. These findings highlight the need to provide dual-income parents with government-led disaster psychological support during COVID-19, such as counseling, education, and mental health management services involving the psychological predictors of work-family conflict. Diverse systematic intervention programs and policy support should also be provided to help them resolve work-family conflict.

Circadian rest-activity rhythm and longitudinal brain changes underlying late-life cognitive decline

AIM

The neurobiological substrates underlying the relationship of circadian rest-activity rhythm (RAR) alteration with accelerated late-life cognitive decline are not clearly understood. In the present study, the longitudinal relationship of objectively measured circadian RAR with in vivo Alzheimer disease (AD) pathologies and cerebrovascular injury was investigated in older adults without dementia.

METHODS

The present study included 129 participants without dementia who participated in the KBASE (Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer's Disease) cohort. All participants underwent actigraphy at baseline and two consecutive [¹¹ C] Pittsburgh compound-B positron emission tomography (PET), [¹⁸ F] fluorodeoxyglucose-PET, magnetic resonance imaging, and Mini-Mental State Examination (MMSE) at baseline and at a 2-year follow-up assessment. The associations of circadian RAR with annualized change in neuroimaging measures including global amyloid-beta retention, AD-signature region cerebral glucose metabolism (AD-CM), and white matter hyperintensity volume were examined.

RESULTS

Delayed acrophase at baseline was significantly associated with greater annualized decline of AD-CM over a 2-year period, but not with that of other neuroimaging measures. In contrast, other circadian RAR parameters at baseline had no association with annualized change of any neuroimaging measures. Annualized decline of AD-CM was also significantly positively associated with the annual change in MMSE scores. Furthermore, a mediation analysis showed that greater reduction in AD-CM mediated the effect of delayed acrophase at baseline on faster decline of MMSE score.

CONCLUSION

The findings indicate that delayed acrophase in late life may cause or predict hypometabolism at AD-signature brain regions, which underlies cognitive decline in the near future.

Enlarged perivascular spaces are associated with decreased brain tau deposition

AIMS

The aim of this study was to investigate the associations of enlarged perivascular spaces (EPVS) in the basal ganglia (BG) and centrum semiovale (CSO) with beta-amyloid (Aβ) and tau deposition in older adults with a diverse cognitive spectrum.

METHODS

A total of 163 (68 cognitively normal and 95 cognitively impaired) older participants underwent [¹¹ C] Pittsburgh compound B and [¹⁸ F] AV-1451 PET, and MRI. EPVS in the BG and CSO and other small vessel disease markers, such as white matter hyperintensities, lacunes, and deep and lobar microbleeds, were assessed.

RESULTS

Increased EPVS in the BG showed a significant association with lower cerebral tau deposition, even after controlling for other small vessel disease markers. Further exploratory analyses showed that this association was significant in cognitively impaired, Aβ-positive, or APOE4-positive individuals, but not significant in the cognitively normal, Aβ-negative, or APOE4-negative participants. In contrast to EPVS in the BG, EPVS in the CSO did not have any relationship with cerebral tau deposition. In addition, none of the two types of EPVS were associated with cerebral Aβ deposition.

CONCLUSION

Brain tau deposition appears to be reduced with increased EPVS in the BG, especially in individuals with cognitive impairment, pathological amyloid burden, or genetic Alzheimer's disease risk.

Association of low meal frequency with decreased in vivo Alzheimer’s pathology

Little is known about the association between meal frequency and Alzheimer’s disease (AD) in humans. We tested the hypothesis that low meal frequency (LMF) is associated with reduced in vivo AD pathology in human brain, and additionally investigated the mediation of serum ghrelin, a hunger-related hormone, for the association. A total of 411 non-demented older adults were systematically interviewed to identify their dietary patterns including meal frequency and underwent multi-modal neuroimaging for cerebral beta-amyloid (Aβ) and tau deposition, glucose metabolism, and cerebrovascular injury. LMF (less than three meals a day) was significantly associated with lower Aβ deposition compared to high meal frequency (HMF). In addition, both LMF and reduced Aβ deposition were significantly related to elevated serum ghrelin. Our findings suggest that LMF may be related to the lower risk of AD through reduced brain amyloid deposition. Additionally, ghrelin appears mediate the association between LMF and lower amyloid deposition.

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Low meal frequency (LMF) relates to lower brain amyloid deposition in human

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Ghrelin mediates the association between LMF and lower amyloid deposition

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LMF may decrease the risk of Alzheimer’s disease (AD) by reducing amyloid deposition

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This finding may be a clue for food intake-based preventive strategy against AD

Spouse bereavement and brain pathologies: A propensity score matching study

AIM

Spouse bereavement is one of life's greatest stresses and has been suggested to trigger or accelerate cognitive decline and dementia. However, little information is available about the potential brain pathologies underlying the association between spouse bereavement and cognitive decline. We aimed to investigate that lifetime spouse bereavement is associated with in vivo human brain pathologies underlying cognitive decline.

METHODS

A total of 319 ever-married older adults between the ages of 61 and 90 years underwent comprehensive clinical assessments and multimodal brain imaging including [¹¹ C] Pittsburgh compound B-positron emission tomography (PET), AV-1451 PET, [¹⁸ F] fluorodeoxyglucose-PET, and magnetic resonance imaging. Participants were classified as experiencing no spouse bereavement or spouse bereavement, and comparisons using propensity score matching (59 cases and 59 controls) were performed.

RESULTS

Spouse bereavement was significantly associated with higher cerebral white matter hyperintensity (WMH) volume compared with no spouse bereavement. Interaction and subsequent subgroup analyses showed that spouse bereavement was significantly associated with higher WMH in the older (>75 years) subgroup and among those with no- or low-skill occupations. In addition, spouse bereavement at 60 years or older affects WMH volume compared with no spouse bereavement, whereas spouse bereavement at younger than 60 years did not. No group differences were observed in other brain pathologies between spouse bereavement categories.

CONCLUSIONS

The findings suggest that the spouse bereavement may contribute to dementia or cognitive decline by increasing cerebrovascular injury, particularly in older individuals and those with no- or low-skill occupations.

Behavioral and Psychological Symptoms and Associated Factors in Community-Dwelling Persons at the First Time of Dementia Diagnosis

Background: Community-dwelling residents at potential risk of dementia and their families have difficulty detecting symptoms of dementia during an outbreak of coronavirus disease-19 (COVID-19). We explored the characteristics of behavioral and psychological symptoms of dementia (BPSD) in community-dwelling persons at the first time of dementia diagnosis and identified their associated variables. Methods: A cross-sectional study using secondary data of dementia diagnosis tests was conducted. Data were reported by professional nurses and clinicians from 355 persons at the first time of dementia diagnosis in South Korea. BPSD and their associated variables were measured with the Neuropsychiatric Inventory, the Korean version of the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD-K) assessment handbook and electronic medical records. Results: The most common symptoms were apathy/indifference (72.1%), followed by irritability/lability (42.8%) and depression/dysphoria (42.0%). Hierarchical regression analyses showed that the strongest factor associated with BPSD was dementia type (β = −0.18, p = 0.001) mostly severer in frontotemporal dementia, followed by activities of daily living dependency (β = 0.15, p = 0.033), and number of medications (β = 0.10, p = 0.048). Conclusion: Providing information based on the study findings to families who are caring for persons at potential risk of dementia, may be able to detect dementia symptoms early and manage appropriate care.

Functional Neural Correlates of Semantic Fluency Task Performance in Mild Cognitive Impairment and Alzheimer's Disease: An FDG-PET Study

BACKGROUND

Total score (TS) of semantic verbal fluency test (SVFT) is generally used to interpret results, but it is ambiguous as to specific neural functions it reflects. Different SVFT strategy scores reflecting qualitative aspects are proposed to identify specific cognitive functions to overcome limitations of using the TS.

OBJECTIVE

Functional neural correlates of the TS as well as the other strategy scores in subjects with mild cognitive impairment (MCI) and Alzheimer's disease (AD) dementia using Fluorine-18-Fluorodeoxyglucose positron emission tomography (FDG-PET).

METHODS

Correlations between various SVFT scores (i.e., TS, mean cluster size, switching (SW), hard switching, cluster switching (CSW)) and cerebral glucose metabolism were explored using voxelwise whole-brain approach. Subgroup analyses were also performed based on the diagnosis and investigated the effects of disease severity on the associations.

RESULTS

Significant positive correlation between TS and cerebral glucose metabolism was found in prefrontal, parietal, cingulate, temporal cortex, and subcortical regions. Significantly increased glucose metabolism associated with the SW were found in similar but smaller regions, mainly in the fronto-parieto-temporal regions. CSW was only correlated with the caudate. In the subgroup analysis conducted to assess different contribution of clinical severity, differential associations between the strategy scores and regional glucose metabolism were found.

CONCLUSION

SW and CSW may reflect specific language and executive functions better than the TS. The SVFT is influenced by brain dysfunction due to the progression of AD, as demonstrated by the SW with larger involvement of temporal lobe for the AD, and CSW with significant association only for the MCI.

Serum zinc levels and in vivo beta-amyloid deposition in the human brain

Background

Despite the known associations between zinc levels and Alzheimer’s disease (AD) dementia and related cognitive impairment, the underlying neuropathological links remain poorly understood. We tested the hypothesis that serum zinc level is associated with cerebral beta-amyloid protein (Aβ) deposition. Additionally, we explored associations between serum zinc levels and other AD pathologies [i.e., tau deposition and AD-signature cerebral glucose metabolism (AD-CM)] and white matter hyperintensities (WMHs), which are measures of cerebrovascular injury.

Methods

A total of 241 cognitively normal older adults between 55 and 90 years of age were enrolled. All the participants underwent comprehensive clinical assessments, serum zinc level measurement, and multimodal brain imaging, including Pittsburgh compound B-positron emission tomography (PET), AV-1451 PET, fluorodeoxyglucose (FDG)-PET, and magnetic resonance imaging. Zinc levels were stratified into three categories: < 80 μg/dL (low), 80 to 90 μg/dL (medium), and > 90 μg/dL (high).

Results

A low serum zinc level was significantly associated with increased Aβ retention. In addition, apolipoprotein E ε4 allele (APOE4) status moderated the association: the relationship between low zinc level and Aβ retention was significant only in APOE4 carriers. Although a low zinc level appeared to reduce AD-CM, the relationship became insignificant on sensitivity analysis including only individuals with no nutritional deficiency. The serum zinc level was associated with neither tau deposition nor the WMH volume.

Conclusions

Our findings suggest that decreased serum zinc levels are associated with elevation of brain amyloid deposition. In terms of AD prevention, more attention needs to be paid to the role of zinc.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-021-00931-3.

The clinical use of blood-test factors for Alzheimer's disease: improving the prediction of cerebral amyloid deposition by the QPLEXTM Alz plus assay kit

Alzheimer's disease (AD) is the leading cause of dementia, and many studies have focused on finding effective blood biomarkers for the accurate diagnosis of this disease. Predicting cerebral amyloid deposition is considered the key for AD diagnosis because a cerebral amyloid deposition is the hallmark of AD pathogenesis. Previously, blood biomarkers were discovered to predict cerebral amyloid deposition, and further efforts have been made to increase their sensitivity and specificity. In this study, we analyzed blood-test factors (BTFs) that can be commonly measured in medical health check-ups from 149 participants with cognitively normal, 87 patients with mild cognitive impairment, and 64 patients with clinically diagnosed AD dementia with brain amyloid imaging data available. We demonstrated that four factors among regular health check-up blood tests, cortisol, triglyceride/high-density lipoprotein cholesterol ratio, alanine aminotransferase, and free triiodothyronine, showed either a significant difference by or correlation with cerebral amyloid deposition. Furthermore, we made a prediction model for Pittsburgh compound B-positron emission tomography positivity, using BTFs and the previously discovered blood biomarkers, the QPLEXTM Alz plus assay kit biomarker panel, and the area under the curve was significantly increased up to 0.845% with 69.4% sensitivity and 90.6% specificity. These results show that BTFs could be used as co-biomarkers and that a highly advanced prediction model for amyloid plaque deposition could be achieved by the combinational use of diverse biomarkers.

Model reduction techniques for the computation of extended Markov parameterizations for generalized Langevin equations

The generalized Langevin equation is a model for the motion of coarse-grained particles where dissipative forces are represented by a memory term. The numerical realization of such a model requires the implementation of a stochastic delay-differential equation and the estimation of a corresponding memory kernel. Here we develop a new approach for computing a data-driven Markov model for the motion of the particles, given equidistant samples of their velocity autocorrelation function. Our method bypasses the determination of the underlying memory kernel by representing it via up to about twenty auxiliary variables. The algorithm is based on a sophisticated variant of the Prony method for exponential interpolation and employs the positive real lemma from model reduction theory to extract the associated Markov model. We demonstrate the potential of this approach for the test case of anomalous diffusion, where data are given analytically, and then apply our method to velocity autocorrelation data of molecular dynamics simulations of a colloid in a Lennard-Jones fluid. In both cases, the velocity autocorrelation function and the memory kernel can be reproduced very accurately. Moreover, we show that the algorithm can also handle input data with large statistical noise. We anticipate that it will be a very useful tool in future studies that involve dynamic coarse-graining of complex soft matter systems.

Validation of the Korean Version of the Anosognosia Questionnaire for Dementia

OBJECTIVE

Anosognosia is a common phenomenon in individuals with dementia. Anosognosia Questionnaire for dementia (AQ-D) is a well-known scale for evaluating anosognosia. This study aimed to establish a Korean version of the AQ-D (AQ-D-K) and to evaluate the reliability and validity of the AQ-D-K in patients with Alzheimer's disease (AD) dementia.

METHODS

We translated the original English version of AQ-D into Korean (AQ-D-K). Eighty-four subjects with very mild or mild AD dementia and their caregivers participated. Reliability of AQ-D-K was assessed by internal consistency and one-month test-retest reliability. Construct validity and concurrent validity were also evaluated.

RESULTS

Internal consistencies of the AQ-D-K patient form and caregiver form were high (Cronbach alpha 0.95 and 0.93, respectively). The test-retest reliability of AQ-D-K measured by intra-class correlation coefficient was 0.84. Three factors were identified: 1) anosognosia of instrumental activity of daily living; 2) anosognosia basic activity of daily living; and 3) anosognosia of depression and disinhibition. AQ-D-K score was significantly correlated with the clinician-rated anosognosia rating scale (ARS), center for epidemiological studies-depression scale (CES-D) and state-trait anxiety inventory (STAI).

CONCLUSION

The findings suggest that the AQ-D-K is a reliable and valid scale for evaluating anosognosia for AD dementia patients using Korean language.

Synergistic Effect of Serum Homocysteine and Diabetes Mellitus on Brain Alterations

BACKGROUND

Both elevated blood homocysteine and diabetes mellitus (DM) are related to cognitive impairments or dementia. A previous study also demonstrated that the association between homocysteine and cognitive decline was much stronger in individuals with DM than in those without DM.

OBJECTIVE

This study aimed to examine the interactive effect of blood homocysteine and DM on brain pathological changes including brain atrophy, amyloid-β and tau deposition, and small vessel disease (SVD) related to cognitive impairments.

METHODS

A total of 430 non-demented older adults underwent comprehensive clinical assessment, measurement of serum homocysteine level, [11C] Pittsburgh Compound B (PiB) PET, [18F] AV-1451 PET, and brain MRI.

RESULTS

The interactive effect of homocysteine with the presence of DM on brain atrophy, especially in aging-related brain regions, was significant. Higher homocysteine concentration was associated with more prominent brain atrophy in individuals with DM, but not in those without DM. In contrast, interaction effect of homocysteine and DM was found neither on Alzheimer's disease (AD) pathologies, including amyloid-β and tau deposition, nor white matter hyperintensity volume as a measure of SVD.

CONCLUSION

The present findings suggest that high blood homocysteine level and DM synergistically aggravate brain damage independently of AD and cerebrovascular disease. With regard to preventing dementia or cognitive decline in older adults, these results support the importance of strictly controlling blood glucose in individuals with hyperhomocysteinemia and lowering blood homocysteine level in those with DM.

Blood Hemoglobin, in-vivo Alzheimer Pathologies, and Cognitive Impairment: A Cross-Sectional Study

Background: Despite known associations between low blood hemoglobin level and Alzheimer's disease (AD) or cognitive impairment, the underlying neuropathological links are poorly understood. We aimed to examine the relationships of blood hemoglobin levels with in vivo AD pathologies (i.e., cerebral beta-amyloid [Aβ] deposition, tau deposition, and AD-signature degeneration) and white matter hyperintensities (WMHs), which are a measure of cerebrovascular injury. We also investigated the association between hemoglobin level and cognitive performance, and then assessed whether such an association is mediated by brain pathologies.

Methods: A total of 428 non-demented older adults underwent comprehensive clinical assessments, hemoglobin level measurement, and multimodal brain imaging, including Pittsburgh compound B-positron emission tomography (PET), AV-1451 PET, fluorodeoxyglucose (FDG)-PET, and magnetic resonance imaging. Episodic memory score and global cognition scores were also measured.

Results: A lower hemoglobin level was significantly associated with reduced AD-signature cerebral glucose metabolism (AD-CM), but not Aβ deposition, tau deposition, or WMH volume. A lower hemoglobin level was also significantly associated with poorer episodic memory and global cognition scores, but such associations disappeared when AD-CM was controlled as a covariate, indicating that AD-CM has a moderating effect.

Conclusion: The present findings suggest that low blood hemoglobin in older adults is associated with cognitive decline via reduced brain metabolism, which seems to be independent of those aspects of AD-specific protein pathologies and cerebrovascular injury that are reflected in PET and MRI measures.

Performance of the QPLEX™ Alz plus assay, a novel multiplex kit for screening cerebral amyloid deposition

Background

Alzheimer’s disease (AD) is an irreversible neurodegenerative disease characterized by the hallmark finding of cerebral amyloid deposition. Many researchers have tried to predict the existence of cerebral amyloid deposition by using easily accessible blood plasma samples, but the effectiveness of such strategies remains controversial.

Methods

We developed a new multiplex kit, the QPLEX™ Alz plus assay kit, which uses proteomics-based blood biomarkers to prescreen for cerebral amyloid deposition. A total of 300 participants who underwent Pittsburgh compound B (PiB)-positron emission tomography (PET) which allows imaging of cerebral amyloid deposition were included in this study. We compared the levels of QPLEX™ biomarkers between patients who were classified as PiB-negative or PiB-positive, regardless of their cognitive function. Logistic regression analysis followed by receiver operating characteristic (ROC) curve analysis was performed. The kit accuracy was tested using a randomized sample selection method.

Results

The results obtained using our assay kit reached 89.1% area under curve (AUC) with 80.0% sensitivity and 83.0% specificity. Further validation of the QPLEX™ Alz plus assay kit using a randomized sample selection method showed an average accuracy of 81.5%.

Conclusions

Our QPLEX™ Alz plus assay kit provides preliminary evidence that it can be used as blood marker to predict cerebral amyloid deposition but independent validation is needed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-020-00751-x.

Genetic associations of in vivo pathology influence Alzheimer's disease susceptibility

INTRODUCTION

Although the heritability of sporadic Alzheimer's disease (AD) is estimated to be 60-80%, addressing the genetic contribution to AD risk still remains elusive. More specifically, it remains unclear whether genetic variants are able to affect neurodegenerative brain features that can be addressed by in vivo imaging techniques.

METHODS

Targeted sequencing analysis of the coding and UTR regions of 132 AD susceptibility genes was performed. Neuroimaging data using 11C-Pittsburgh Compound B positron emission tomography (PET), 18F-fluorodeoxyglucose PET, and MRI that are available from the KBASE (Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer's disease) cohort were acquired. A total of 557 participants consisted of 336 cognitively normal (CN) adults, 137 mild cognitive impairment (MCI), and 84 AD dementia (ADD) groups.

RESULTS

We called 5391 high-quality single nucleotide variants (SNVs) on AD susceptibility genes and selected significant associations between variants and five in vivo AD pathologies: (1) amyloid β (Aβ) deposition, (2) AD-signature region cerebral glucose metabolism (AD-Cm), (3) posterior cingulate cortex (PCC) cerebral glucose metabolism (PCC-Cm), (4) AD-signature region cortical thickness (AD-Ct), and (5) hippocampal volume (Hv). The association analysis for common variants (allele frequency (AF) > 0.05) yielded several novel loci associated with Aβ deposition (PIWIL1-rs10848087), AD-Cm (NME8-rs2722372 and PSEN2-rs75733498), AD-Ct (PSEN1-rs7523) and, Hv (CASS4-rs3746625). Meanwhile, in a gene-based analysis for rare variants (AF < 0.05), cases carrying rare variants in LPL, FERMT2, NFAT5, DSG2, and ITPR1 displayed associations with the neuroimaging features. Exploratory voxel-based brain morphometry between the variant carriers and non-carriers was performed subsequently. Finally, we document a strong association of previously reported APOE variants with the in vivo AD pathologies and demonstrate that the variants exert a causal effect on AD susceptibility via neuroimaging features.

CONCLUSIONS

This study provides novel associations of genetic factors to Aβ accumulation and AD-related neurodegeneration to influence AD susceptibility.

Serum Uric Acid, Alzheimer-Related Brain Changes, and Cognitive Impairment

Background

Despite known associations of lower serum uric acid (UA) with Alzheimer’s disease (AD) dementia or AD-related cognitive impairment, little is known regarding the underlying patho-mechanisms. We aimed to examine the relationships of serum UA with in vivo AD pathologies including cerebral beta-amyloid (Aβ) and tau deposition, AD-signature region cerebral glucose metabolism (AD-CM), and white matter hyperintensities (WMH). We also investigated the association between serum UA and cognitive performance, and then assessed whether such an association is mediated by the brain pathologies.

Methods

A total of 430 non-demented older adults underwent comprehensive clinical assessments, measurement of serum UA level, and multimodal brain imaging, including Pittsburgh compound B-positron emission tomography (PET), AV-1451 PET, fluorodeoxyglucose (FDG)-PET, and magnetic resonance imaging scans. Mini-Mental State Examination (MMSE) and word list recall (WLR) test scores were used to measure cognitive performance.

Results

Serum UA level was significantly associated with AD-CM, but not with Aβ deposition, tau deposition, or WMH volume. Serum UA levels also had significant association with WLR and marginal association with MMSE; such associations disappeared when AD-CM was controlled as a covariate, indicating that AD-CM has a mediating effect.

Conclusion

The findings of the present study indicate that there is an association of low serum UA with AD-related cerebral hypometabolism, and whether this represents a causal relationship remains to be determined.

Comparison of Amyloid Positivity Rate and Accumulation Pattern between Amnestic and Non-Amnestic Type Mild Cognitive Impairment

OBJECTIVE

We aimed to compare cerebral beta-amyloid protein (Aβ) positivity rate and amyloid accumulation pattern on amyloid positron emission tomography (PET) between mild cognitive impairment (MCI) subtypes, i.e. amnestic mild cognitive impairment (aMCI) and non-amnestic mild cognitive impairment (naMCI).

METHODS

The study participants were 34 naMCI patients and age-, sex- and education-matched 68 aMCI patients (1:2 ratio) who visited the Dementia and Age-Associated Cognitive Decline Clinic of the Seoul National University Hospital. All participants received comprehensive clinical and neuropsychological assessments and [¹⁸F] florbetaben PET.

RESULTS

Aβ positivity rate of naMCI group (26.5%) was significantly lower than that of aMCI group (64.7%). Among Aβ positive individuals, there was no difference in Aβ accumulation pattern between naMCI and aMCI.

CONCLUSION

The findings suggest that MCI subtypes based on impaired cognitive domains have a differential association with brain Aβ deposition, a core pathology of AD. Amnestic subtype of MCI are more closely associated with cerebral Aβ deposition compared to nonamnestic subtype. In contrast, the pattern of amyloid deposition does not appear to have any difference between the subtypes.

[The DIGG risk score : A risk predictive model of perioperative mortality after elective treatment of intact abdominal aortic aneurysms in the DIGG register]

OBJECTIVE

The aim of the study was to develop a specific risk score for the aortic register of the German Institute for Vascular Health Care Research (DIGG) of the German Society for Vascular Surgery and Vascular Medicine (DGG) for the prediction of postoperative mortality in elective treatment of intact abdominal aortic aneurysms (iAAA). The score should also enable a risk-adjusted presentation of the register results in the near future.

METHODS

The method of binary logistic regression analysis was used to calculate the model. The data from 10,404 patients were included in the analysis, of whom 7870 (75.6%) were treated by endovascular (EVAR) and 2534 (24.4%) by open (OR) aortic repair. It was examined which factors have an independent influence on hospital mortality and the effect size was determined as a score.

RESULTS

For EVAR, the influencing factors with their effect sizes (score in brackets) were: age >85 years (2), female gender (2), juxtarenal AAA (5), maximum diameter >65 mm (2), diabetes mellitus (2), American Society of Anesthesiologists (ASA) score >3 (2), cardiac comorbidities (3) and renal insufficiency stage >3 (5). For OR the factors were: age >80 years (2), female gender (2), juxtarenal AAA (2), ASA score >3 (3), previous myocardial infarction (2), renal comorbidities (3) and previous stroke (2). The estimated hospital mortality was calculated for the individual case from the sum of the risk factors (scores). The accuracy of the model (correlation between observed and expected results) was determined using the receiver operating characteristic (ROC) curve. An area under the curve (AUC) of 0.817 (confidence interval 0.789-0.844) demonstrated an excellent discrimination. In a validation group of 3831 patients, the good agreement between observed and calculated results was confirmed.

CONCLUSION

The DIGG risk score can predict risk-adjusted hospital mortality after EVAR and OR of iAAA in the DIGG register. Improvements with respect to the prediction are desirable for OR and should be strived for by extending the model in the future.

Coffee intake and decreased amyloid pathology in human brain

Several epidemiological and preclinical studies supported the protective effect of coffee on Alzheimer's disease (AD). However, it is still unknown whether coffee is specifically related with reduced brain AD pathologies in human. Hence, this study aims to investigate relationships between coffee intake and in vivo AD pathologies, including cerebral beta-amyloid (Aβ) deposition, the neurodegeneration of AD-signature regions, and cerebral white matter hyperintensities (WMH). A total of 411 non-demented older adults were included. Participants underwent comprehensive clinical assessment and multimodal neuroimaging including [¹¹C] Pittsburgh compound B-positron emission tomography (PET), [¹⁸F] fluorodeoxyglucose PET, and magnetic resonance imaging scans. Lifetime and current coffee intake were categorized as follows: no coffee or <2 cups/day (reference category) and ≥2 cups/day (higher coffee intake). Lifetime coffee intake of ≥2 cups/day was significantly associated with a lower Aβ positivity compared to coffee intake of <2 cups/day, even after controlling for potential confounders. In contrast, neither lifetime nor current coffee intake was not related to hypometabolism, atrophy of AD-signature region, and WMH volume. The findings suggest that higher lifetime coffee intake may contribute to lowering the risk of AD or related cognitive decline by reducing pathological cerebral amyloid deposition.

Vascular risk modulates the relationship between cerebral amyloid deposition and subjective memory complaints

PURPOSE

We aimed to investigate the relationships of cerebral amyloid beta (Aβ) deposition and neurodegeneration (ND) with subjective memory complaints (SMCs) in cognitively normal (CN) individuals, focusing specially on the modulating effects of vascular risk (VR) on those relationships.

PARTICIPANTS AND METHODS

A total of 230 CN elderly individuals underwent comprehensive clinical assessments including the Subjective Memory Complaints Questionnaire (SMCQ), VR assessment, and multimodal brain imaging including [¹¹C] Pittsburgh compound B positron emission tomography (PET), [¹⁸F] fluorodeoxyglucose-PET, and magnetic resonance imaging.

RESULTS

We found a significant overall positive association between cerebral Aβ retention and SMCQ score. In addition, we found a significant cerebral Aβ retention × VR interaction effect on the SMCQ score. Subgroup analyses showed that the Aβ-SMC association was found only in VR-negative, and not in VR-positive, individuals. We found no relationship between ND and SMCQ.

CONCLUSION

Our findings suggest that SMC in CN elderly individuals reflects early accumulation of Aβ in the brain. Given the modulating effect of VR on the Aβ-SMC relationship, SMC can be used as a meaningful marker of early Aβ deposition in individuals without VR.

Tyrosine kinase inhibition increases the cell surface localization of FLT3-ITD and enhances FLT3-directed immunotherapy of acute myeloid leukemia

The fms-related tyrosine kinase 3 (FLT3) receptor has been extensively studied over the past two decades with regard to oncogenic alterations that do not only serve as prognostic markers but also as therapeutic targets in acute myeloid leukemia (AML). Internal tandem duplications (ITDs) became of special interest in this setting as they are associated with unfavorable prognosis. Because of sequence-dependent protein conformational changes FLT3-ITD tends to autophosphorylate and displays a constitutive intracellular localization. Here, we analyzed the effect of tyrosine kinase inhibitors (TKIs) on the localization of the FLT3 receptor and its mutants. TKI treatment increased the surface expression through upregulation of FLT3 and glycosylation of FLT3-ITD and FLT3-D835Y mutants. In T cell-mediated cytotoxicity (TCMC) assays, using a bispecific FLT3 × CD3 antibody construct, the combination with TKI treatment increased TCMC in the FLT3-ITD-positive AML cell lines MOLM-13 and MV4-11, patient-derived xenograft cells and primary patient samples. Our findings provide the basis for rational combination of TKI and FLT3-directed immunotherapy with potential benefit for FLT3-ITD-positive AML patients.

Conductivity fluctuations in proton-implanted ZnO microwires

Electric noise can be an important limitation for applications of conducting elements in the nanometer size range. The intrinsic electrical noise of prospective materials for opto-spintronics applications like ZnO has not yet been characterized. In this study, we have investigated the conductivity fluctuations in 10 nm thick current paths produced by proton implantation of ZnO microwires at room temperature. The voltage noise under a constant dc current bias in undoped, as well as in Li-doped microwires, is characterized by [Formula: see text] power spectra with [Formula: see text]. The noise intensity scales with the square of the bias current pointing to bias-independent resistivity fluctuations as a source of the observed noise. The normalized power spectral density appears inversely proportional to the number of carriers in the probed sample volume, in agreement with the phenomenological Hooge law. For the proton-implanted ZnO microwire and at 1 Hz we obtain a normalized power spectral density as low as [Formula: see text] Hz(-1).

HIV-1 Aspartic Proteinase: High-Level Production and Automated Fluorometric Screening Assay of Inhibitors

The 99-amino-acid HIV-1 aspartic proteinase was expressed to high levels in Escherichia coli using a T7 expression system. About 50% of the insoluble material after sonication of the bacteria was composed of aggregated proteinase. Subsequent renaturation and purification yielded large quantities of a homogeneous enzyme able to cleave various heptapeptidic substrates in vitro with a Km around 2.5 mM. A fluorometric assay has been devised to allow automated screening of HIV proteinase inhibitors based on an analogous renin assay. We used the synthetic intramolecularly quenched fluorogenic substrate Suc-TLNFPIS-4MCA based on the heptapeptide TLNFPIS, which encompasses the proteinase/reverse transcriptase junction, coupled to the fluorophore 7-amino-4-methylcoumarin and blocked at the amino-terminus by a succinyl group. The enzyme cleaves the substrate between phenylalanine and proline, and conditions were optimized for liberation of 7AMC from the generated PIS-4MCA with aminopeptidase M as secondary enzyme. 7AMC was monitored with a microplate fluorescence scanner. The known aspartic proteinase inhibitor pepstatin A consistently gave Ki = 2 × 10−6M. Other synthetic and natural compounds are currently being tested.

Proteomic analysis of the TerC interactome: Novel links to tellurite resistance and pathogenicity

The tellurite resistance gene operon (ter) is widely spread among bacterial species, particularly pathogenic species. The ter operon has been implicated in tellurite resistance, phage inhibition, colicine resistance, and pathogenicity. The TerC protein represents one of the key proteins in tellurite resistance and shows no significant homology to any protein of known function. So far, there is no experimental evidence for TerC interaction partners. In this study, proteomic-based methods, including blue native electrophoresis and co-immunoprecipitation combined with LC-MS/MS, have been used to identify TerC interaction partners and thus providing indirect evidence for tentative functions of TerC in Escherichia coli. An interactome has been constructed and robust physical interaction of integral membrane protein TerC with TerB, DctA, PspA, HslU, and RplK has been shown. The TerC-TerB complex appears to act as a central unit that may link different functional modules with biochemical activities of C4-dicarboxylate transport, inner membrane stress response (phage shock protein regulatory complex), ATPase/chaperone activity, and proteosynthesis. In previous reports, it was hypothesized that a transmembrane unit formed by TerC protein may interact with the TerD family, but herein neither TerD nor TerE proteins were identified as TerC complex components. We propose that TerD/TerE participates in tellurite resistance through TerC-independent action.

2-amino-N-(2,6-dichloropyridin-3-yl)acetamide derivatives as a novel class of HBV capsid assembly inhibitor

Capsid structure is crucial for the maturation and maintenance of the stable hepatitis B virion. Therefore, chemicals that inhibit capsid assembly might potentially act as potent antiviral compounds. However, only a few chemicals are known to block the capsid assembly process and further viral proliferation. In this study, we present a novel family of capsid assembly inhibitors that act against hepatitis B virus (HBV). Based on X-ray crystallographic data of the HBV core protein (Cp), we built dimer and hexamer structural models to be used in library searches. Several chemicals in the 2-amino-N-(2,6-dichloropyridin-3-yl)acetamide family were predicted to have high affinity for the groove structure in Cp. Using in vitro assembly and the HepG2.2.15 cell culture test, we verified that these chemicals demonstrated inhibitory effects on capsid assembly. Furthermore, we investigated the combinatorial effects of these assembly inhibitor chemicals with lamivudine and revealed that, in combination, they have synergistic inhibitory effects on decreasing viral concentration. We propose that these inhibitors could be utilized as an effective combination treatment against HBV infection.

Notch1 increases Snail expression under high reactive oxygen species conditions in hepatocellular carcinoma cells

Notch1 and reactive oxygen species (ROS) modulate important pathways associated with tumor development and progression. Notably, Notch1 expression is upregulated in 41.8% of hepatocellular carcinoma (HCC) patients and ROS levels increases as HCC progresses from Grade I to Grade III. It has been established that Notch1 and ROS modulate Snail expression in malignant tumors; however, the mechanism regulating Snail protein expression is not yet known. In this study, we observed that Notch1 and ROS cooperatively increase the levels of Snail protein in Huh7 (hepatoma) cells. On its own, signaling through Notch1 increases transcription of Snail without changing protein levels. In contrast, the combined activation of the Notch1 and ROS-induced phosphoinositide 3-kinase/Akt (PI3K/Akt) signaling pathways resulted in the high expression of Snail protein. This increase in Snail expression was associated with increased Huh7 cells invasiveness. Furthermore, we observed that correlation between Snail and Notch1 expression was the strongest in advanced grade HCC tissue. In conclusion, Notch1 and ROS-induced PI3K/Akt signals cooperatively increase Snail expression and may induce malignancy in HCC.

Single-molecule microscopy of the green fluorescent protein using simultaneous two-color excitation

In vivo microscopy of the Green Fluorescent Protein (GFP), the most important label in cell biology, with single-molecule sensitivity is hampered by an insufficient signal-to-noise ratio. A significant improvement is obtained with a novel two-color excitation technique. The picture clearly shows the increased brightness of GFP in in vitro single-molecule assays and in live-cell microscopy under two-color illumination (upper cell) as compared to normal illumination (lower cell).