Johan Sundelöf

Impaired insulin secretion increases the risk of Alzheimer disease

Objective: Subjects with diabetes are reported to have an increased risk of dementia and cognitive impairment. However, the underlying causes remain unknown. We investigated the longitudinal associations between midlife insulin secretion, glucose metabolism, and the subsequent development of Alzheimer disease (AD) and dementia. Methods: The population-based Uppsala Longitudinal Study of Adult Men started 1970 when the 2,322 participants were 50 years old. Investigation at baseline included determinations of acute insulin response and glucose tolerance using the IV glucose tolerance test and Homeostasis Model Assessment insulin resistance index. During a median follow up of 32 years, 102 participants were diagnosed with AD, 57 with vascular dementia, and 394 with any dementia or cognitive impairment. Associations were analyzed using Cox proportional hazard models. Results: A low insulin response at baseline was associated with a higher cumulative risk of AD (hazard ratio for 1 SD decrease, 1.31; 95% CI, 1.10–1.56) also after adjustment for age, systolic blood pressure, body mass index, serum cholesterol, smoking, education level, and insulin resistance. This association was stronger in subjects without the APOE ε4 allele. Impaired glucose tolerance increased the risk of vascular dementia (hazard ratio for 1 SD decrease, 1.45; 95% CI, 1.05–2.00) but not AD. Impaired insulin secretion, glucose intolerance, and estimates of insulin resistance were all associated with higher risk of any dementia and cognitive impairment. Conclusions: In this longitudinal study, impaired acute insulin response at midlife was associated with an increased risk of Alzheimer disease (AD) up to 35 years later suggesting a causal link between insulin metabolism and the pathogenesis of AD.

Plasma β Amyloid and the Risk of Alzheimer Disease and Dementia in Elderly Men : A Prospective, Population-Based Cohort Study

BACKGROUND Beta amyloid (Abeta) protein accumulates in the brains of individuals with Alzheimer disease (AD) and is detectable in cerebrospinal fluid and plasma. OBJECTIVE To examine plasma levels of Abeta peptides Abeta(40) and Abeta(42) as predictors of incident AD and other types of dementia. DESIGN Prospective, population-based cohort study. SETTING The Uppsala Longitudinal Study of Adult Men. PARTICIPANTS Plasma Abeta(40) and Abeta(42) levels were analyzed as predictors of incident AD in 1045 men at age 70 years and 680 men at age 77 years using Cox proportional hazards analyses. Alzheimer disease and other types of dementia were diagnosed by standardized screening, clinical evaluation, and medical record review. MAIN OUTCOME MEASURES Hazard ratios of AD (primary outcome) and vascular dementia or other dementia (secondary outcomes) according to baseline levels of plasma Abeta(40) and Abeta(42). RESULTS From the age of 77 years at baseline, 46 individuals developed AD at follow-up (median, 5.3 years). A low plasma Abeta(40) level at age 77 years was associated with higher incidence of AD. The multivariate-adjusted hazard ratio was 4.87 (95% confidence interval, 1.63-14.6) for the lowest Abeta(40) tertile compared with the highest tertile. On follow-up from age 70 years at baseline (median, 11.2 years), 82 individuals developed AD. Plasma Abeta(40) and Abeta(42) levels measured at age 70 years were not significantly associated with incident AD. CONCLUSIONS Low plasma Abeta(40) levels predicted incident AD in elderly men independently of potential confounders. Plasma Abeta(42) levels were not significantly associated with AD incidence. The clinical value of Abeta measurement in plasma remains to be established in future studies.

The normal equilibrium between CSF and plasma amyloid beta levels is disrupted in Alzheimer's disease

Amyloid-beta (Abeta) with 40 (Abeta40) and 42 (Abeta42) amino acids, the main components of amyloid plaques in the Alzheimers disease (AD) brain, can be measured in human cerebrospinal fluid (CSF) and plasma. Whereas CSF Abeta42 is decreased in AD, some studies have reported changed plasma Abeta levels in AD and in subjects with mild cognitive impairment (MCI). To this date it is unclear if and how CSF and plasma levels of Abeta correlate with each other in healthy individuals, albeit earlier studies on AD patients found no correlation between CSF and plasma Abeta. We have measured Abeta40 and Abeta42 in paired CSF and plasma samples from patients with AD (n=39), MCI (n=29) and healthy control subjects (n=18). We observed a clear correlation between CSF and plasma levels for both Abeta40 and Abeta42 in healthy individuals, whereas no such correlation could be seen for AD or MCI cases. Similarly to other studies we also found low levels of Abeta42 in AD CSF, whereas there were no significant differences in plasma Abeta levels between the diagnostic groups. Our findings suggest that the normal equilibrium between CSF and plasma Abeta may be disrupted with the initiation of amyloid deposition in the brain.

Genetic Analysis of Alzheimer's Disease in the Uppsala Longitudinal Study of Adult Men

Background/Aims: Genetic factors influencing common complex conditions have proven difficult to identify, and data from numerous investigations have provided incomplete conclusions as to the identity of these genes. Here we aimed to identify susceptibility genes for late-onset Alzheimer’s disease (AD). Methods: The case-control analysis included samples from 86 AD patients and 404 cognitively healthy controls selected from the Uppsala Longitudinal Study of Adult Men (ULSAM). In the incidence analysis, all 1,088 genotyped ULSAM participants were included. DNA samples from ULSAM participants were analyzed for 2,578 single nucleotide polymorphisms (SNP) within 368 genes. The selection of genes tested for association to AD within this cohort was based on genes previously implicated in conditions with relevance to ULSAM, such as dementia, cardiovascular disease, diabetes and metabolic syndrome, osteoporosis, and cancer. Results/Conclusion: Association analysis revealed 82 genes containing at least 1 significant SNP at p < 0.05 with association to AD. Only 20 genes remained significant after a permutation test to correct for multiple comparisons within individual genes. Using publicly available data from 2 genome-wide association (GWA) studies and linkage disequilibrium data from HapMap, we attempted to replicate the AD association identified in ULSAM. In addition to apolipoprotein E, we were able to replicate 5 other genes in both GWA studies at p < 0.05.

Systemic Inflammation and the Risk of Alzheimer's Disease and Dementia: A Prospective Population-Based Study

Inflammation is suggested to be involved in the pathogenesis of Alzheimers disease (AD). Serum interleukin-6 (IL-6) and high sensitivity serum reactive protein C (hsCRP) as markers of systemic inflammation were analyzed at two examinations of the ULSAM-study, a longitudinal, community-based study of elderly men (age 70, n = 1062 and age 77, n = 749). In addition, serum amyloid protein A (SAA) and urinary prostaglandin F2alpha (PGF2alpha) metabolite levels were analyzed at age 77 in this cohort. Two serial samples (at ages 70 and 77) were available from 704 individuals. Using Cox regression analyses, associations between serum IL-6, hsCRP, SAA and PGF2alpha metabolite levels and risk of AD, any type of dementia (all-cause dementia) and non-AD dementia were analyzed. On follow-up (median, 11.3 years) in the age 70 cohort, 81 subjects developed AD and 165 subjects developed all-cause dementia. Serum IL-6, hsCRP, SAA, or PGF2alpha levels were not associated with risk of AD. At age 70, high IL-6 levels were associated with an increased risk of non-AD dementia (Hazard ratio 2.21 for above vs. below/at median, 95%confidence interval 1.23-3.95, p-value = 0.008). A longitudinal change in CRP or IL-6 levels was not associated with AD ordementia. In conclusion, Serum IL-6, hsCRP, SAA, and PGF2alpha levels are not associated with the risk of AD. High serum IL-6 levels may be associated with increased risk of non-AD dementia.

Serum cystatin C and the risk of Alzheimer disease in elderly men.

Background: Multiple lines of research suggest that increased cystatin C activity in the brain protects against the development of Alzheimer disease (AD). Methods: Serum cystatin C levels were analyzed at two examinations of the Uppsala Longitudinal Study of Adult Men, a longitudinal, community-based study of elderly men (age 70 years, n = 1,153 and age 77 years, n = 761, a subset of the age 70 examination). Cox regressions were used to examine associations between serum cystatin C and incident AD. AD cases were identified by cognitive screening and comprehensive medical chart review in all subjects. Results: On follow-up (median 11.3 years), 82 subjects developed AD. At age 70 years, lower cystatin C was associated with higher risk of AD independently of age, APOE4 genotype, glomerular filtration rate, diabetes, hypertension, stroke, cholesterol, body mass index, smoking, education level, and plasma amyloid-β protein 40 and 42 levels (hazard ratio [HR] for lowest [<1.12 μmol/L] vs highest [>1.30 μmol/L] tertile = 2.67, 95% CI 1.22–5.83, p < 0.02). The results were similar at age 77 years (43 participants developed AD during follow-up). Furthermore, a 0.1-μmol/L decrease of cystatin C between ages 70 and 77 years was associated with a 29% higher risk of incident AD (HR 1.29, 95% CI 1.03–1.63, p < 0.03). Conclusions: Low levels of serum cystatin C precede clinically manifest Alzheimer disease (AD) in elderly men free of dementia at baseline and may be a marker of future risk of AD. These findings strengthen the evidence for a role for cystatin C in the development of clinical AD. GLOSSARY: Aβ40 = amyloid-β protein 40; Aβ42 = amyloid-β protein 42; AD = Alzheimer disease; BMI = body mass index; GFR = glomerular filtration rate; HR = hazard ratio; ICD = International Classification of Diseases; ULSAM = Uppsala Longitudinal Study of Adult Men.

Cognitive function and risk of stroke in elderly men.

Objective: Vascular risk factors are associated with ischemic changes in the cerebral white matter. We studied the predictive value of cognitive test performance especially related to subcortico-frontal pathways, together with a cognitive screening test, for later incidence of fatal or nonfatal stroke or TIAs and stroke subtypes. Methods: A sample of 930 70-year-old men without previous stroke/TIA from the community-based Uppsala Longitudinal Study of Adult Men was investigated at baseline using Trail Making Tests (TMT) A and B and the Mini-Mental State Examination (MMSE). Results: During up to 13 years of follow-up, 166 men developed a stroke or TIA; 105 participants had a brain infarction. In Cox proportional hazards analyses adjusting for education, social group, and traditional cardiovascular risk factors, a 1-SD increase in TMT-B time was associated with a higher risk for brain infarction (hazard ratio 1.48, 95% confidence interval 1.11–1.97). The risk of brain infarction was more than threefold higher in the highest (TMT-B = 146–240 s) compared to the lowest (TMT-B = 43–84 s) TMT-B quartile. TMT-A and MMSE results were not consistently related to stroke outcomes. Conclusion: Impaired performance in elderly men measured by Trail Making Test B, a cognitive test especially reflecting subcortico-frontal activities, was an independent predictor of subsequent brain infarction in this community-based sample of elderly men. Our results extend previous findings of cognitive decline as an independent predictor of stroke and indicate that the risk of brain infarction is increased already in the subclinical phase of cognitive deficit.

Higher cathepsin B levels in plasma in Alzheimer's disease compared to healthy controls.

Cathepsin B is suggested to be involved in amyloid-β (Aβ) processing and Alzheimers disease (AD). Studies of cathepsin B levels in plasma and cerebrospinal fluid (CSF) have not been previously performed. We examined cathepsin B levels in plasma and CSF samples in persons with AD, mild cognitive impairment (MCI), and healthy controls in order to test the hypothesis that cathepsin B levels can discriminate persons with AD or MCI from healthy controls. Cathepsin B, Cystatin C, Aβ1-40 and Aβ1-42, total tau, phosphorylated tau, and albumin levels in plasma and CSF were analyzed by ELISA (Cathepsin B) turbidimetry (cystatin C), xMAP Luminex technology (Aβ1-40 and Aβ1-42 and tau), and Cobas C501 analyzer (albumin) in persons with AD (n=101), MCI (n=84), and healthy control subjects (n=28). Plasma cathepsin B levels were higher in persons with AD compared to healthy controls, both in unadjusted models and in multivariable models adjusting for age, gender, APOE genotype, cystatin C, and albumin levels: Odds ratio (OR) for AD per 1 SD of plasma cathepsin B; 2.04, 95% confidence interval (CI); 1.01-4.14, p= 0.05. There was no difference between diagnostic groups in cathepsin B levels in CSF: OR for AD per 1 SD of CSF cathepsin B; 0.93, 95% CI; 0.37-2.30, p= 0.87. Plasma cathepsin B levels were higher in persons with AD compared to healthy controls whereas there was no difference between diagnostic groups in cathepsin B levels in CSF. Further investigation of cathepsin B as a predictor of AD is warranted.

Cystatin C Levels are Positively Correlated with both Aβ42 and Tau Levels in Cerebrospinal Fluid in Persons with Alzheimer's Disease, Mild Cognitive Impairment, and Healthy Controls

Cystatin C is suggested to be involved in neurodegeneration and the development of Alzheimers disease (AD) by binding to soluble amyloid-beta (Abeta) peptides. Studies of cystatin C levels in cerebrospinal fluid (CSF) in relation to risk of AD are conflicting and relations between cystatin C, Abeta42, and tau levels in CSF in AD, mild cognitive impairment (MCI), and healthy controls are unknown. The objective of this study was to investigate cystatin C, Abeta42, and tau levels in CSF in AD, MCI, and controls. As a secondary aim, the relationships between cystatin C, Abeta42, and tau levels across disease groups were investigated. Cystatin C, Abeta42, total tau, and phosphorylated tau levels in CSF were analyzed by turbidimetry (cystatin C) and xMAP Luminex technology (Abeta and tau) in persons with AD (n=101), MCI (n=84), and healthy control subjects (n=28). Mean cystatin C levels were similar in cases of AD (5.6 micromol/L +/- 1.7), MCI (5.4 micromol/L +/- 1.48), and controls (5.6 micromol/L +/- 1.6). However, CSF cystatin C levels were strongly and positively correlated with total tau and phosphorylated tau levels (r=0.61-0.81, p< 0.0001) and Abeta42 (r=0.35-0.65, p< 0.001) independent of age, gender, and APOE genotype. Mean CSF cystatin C levels did not differ between patients with AD and MCI and healthy controls. Interestingly, cystatin C levels were positively correlated with both tau and Abeta42 levels in CSF independent of age, gender, and APOE genotype.

Systemic tocopherols and F2-isoprostanes and the risk of Alzheimer's disease and dementia: a prospective population-based study

Oxidative stress in the brain is suggested to be involved in the pathophysiology of Alzheimers disease (AD). In this study, serum alpha- and gamma-tocopherol, the two major systemic antioxidants, were analyzed at two examinations of the ULSAM-study, a longitudinal, community-based study of elderly men (age 70, n = 616 and age 77, n = 761). In addition, urinary F2-isoprostane levels, as markers of systemic oxidative stress, were analyzed at the age of 77 in this cohort (n = 679). Cox regression analyses were used to examine associations between serum alpha-, gamma-tocopherol and urinary F2-isoprostane levels and AD, any type of dementia (all-cause dementia) and non-AD dementia. On follow-up (median, 12.3 years), 40 subjects developed AD and 86 subjects developed all-cause dementia. Serum alpha- and gamma-tocopherol or urinary F2-isoprostane levels were not associated with the future risk of AD or dementia. In conclusion, systemic serum alpha- and gamma-tocopherol and urinary F2-isoprostane levels are not associated with the future risk of AD or dementia and do not seem to be useful predictors of clinical AD or dementia.