Relationship between serum alpha 1-antichymotrypsin and Alzheimer's disease

Assessing candidate serum biomarkers for Alzheimer's disease: a longitudinal study

Because of the growing impact of late onset cognitive loss, considerable effort has been directed toward the development of improved diagnostic techniques for Alzheimer's disease (AD) that may pave the way for earlier (and more effective) therapeutic efforts. Serum-based biomarkers are the least expensive and invasive modality for screening and routine monitoring. We systematically reviewed the literature to assemble a list of serum biomarkers relevant to AD. In parallel, we conducted a proteomic LC-MS/MS analysis of serum collected from neurologically normal subjects and subjects with mild cognitive impairment (MCI) and early AD (n = 6 in all). Complement C3 and alpha-2-macroglobulin were identified from both the literature review and our proteomic screen for further validation. For these two candidates, ELISA was performed on serum collected from a small independent cohort of subjects for longitudinal analysis. Serum was serially collected from neurologically normal subjects (n = 5) and subjects with MCI who were subsequently followed for a period of two years (n = 5) and regrouped into stable MCI and progressive MCI or AD (n = 6). The ability of each marker to predict which subjects with MCI would progress to dementia and which would remain cognitively stable was assessed. Patients with probable cerebral amyloid angiopathy were also identified (n = 3). This preliminary analysis tested the most-promising serum protein biomarkers for AD and we concluded that none are yet ready for use in the clinical diagnosis and management of dementia. However, a more thorough assessment in longitudinal studies with higher statistical power is warranted.

Biomarkers of Alzheimer's disease

Although a battery of neuropsychological tests is often used in making a clinical diagnosis of Alzheimer's disease (AD), definitive diagnosis still relies on pathological evaluation at autopsy. The identification of AD biomarkers may allow for a less invasive and more accurate diagnosis as well as serve as a predictor of future disease progression and treatment response. Importantly, biomarkers may also allow for the identification of individuals who are already developing the underlying pathology of AD such as plaques and tangles yet who are not yet demented, i.e. "preclinical" AD. Attempts to identify biomarkers have included fluid and imaging studies, with a number of candidate markers showing significant potential. More recently, better reagent availability and novel methods of assessment have further spurred the search for biomarkers of AD. This review will discuss promising fluid and imaging markers to date.

Peptides and proteins in plasma and cerebrospinal fluid as biomarkers for the prediction, diagnosis, and monitoring of therapeutic efficacy of Alzheimer's disease

Alzheimer's disease (AD) affects millions of persons worldwide. Earlier detection and/or diagnosis of AD would permit earlier intervention, which conceivably could delay progression of this dementing disorder. In order to accomplish this goal, reliable and specific biomarkers are needed. Biomarkers are multidimensional and have the potential to aid in various facets of AD such as diagnostic prediction, assessment of disease stage, discrimination from normally cognitive controls as well as other forms of dementia, and therapeutic efficacy of AD drugs. To date, biomarker research has focused on plasma and cerebrospinal fluid (CSF), two bodily fluids believed to contain the richest source of biomarkers for AD. CSF is the fluid surrounding the central nervous system (CNS), and is the most indicative obtainable fluid of brain pathology. Blood plasma contains proteins that affect brain processes from the periphery, as well as proteins/peptides exported from the brain; this fluid would be ideal for biomarker discovery due to the ease and non-invasive process of sample collection. However, it seems reasonable that biomarker discovery will result in combinations of CSF, plasma, and other fluids such as urine, to serve the aforementioned purposes. This review focuses on proteins and peptides identified from CSF, plasma, and urine that may serve as biomarkers in AD.

Eight-residue Abeta peptides inhibit the aggregation and enzymatic activity of Abeta42

Insoluble Abeta1-42 is the main component of the amyloid plaque. We have previously demonstrated that exposure to low pH can confer the molten globule state on soluble Abeta1-42 in vitro [Biochem. J. 361 (2000) 547] and unfolding experiments with guadinine hydrochloride (GdnHCl) have now confirmed this observation. The molten globule state of the protein has many biological properties and understanding the mechanisms of its formation is an important step in devising a therapeutic strategy for Alzheimer's disease (AD). We therefore investigated the ability of a series of synthetic eight-residue peptides derived from Abeta1-42 to inhibit the acid-induced aggregation of Abeta1-42 and identified the potent peptides to be Abeta15-22, Abeta16-23 and Abeta17-24. A1-antichymotrypsin, a member of the serine proteinase inhibitor (serpin) family is another major component of the amyloid plaque. In the present study, we investigated the proteolytic activity of Abeta1-42 against casein at different pHs. Chemical modification of amino acid residues in Abeta1-42 indicated that serine and histidine residues, but not aspartic acid, are necessary for enzymatic activity, suggesting that it is a serine proteinase. Amino acid substitution studies indicate that glutamic acids at positions 11 and 22 participate indirectly in proteolysis and we surmise that amino acid residues 29-42 are required to stabilize the conformer. A study of metal ions suggested that Cu2+ affected the enzymatic activity, but Zn2+ and Fe2+ did not. Interestingly, Abeta14-21 and Abeta15-22 were the only peptides that inhibited the proteolytic activity of Abeta42. Therefore, Abeta15-22 may control both aggregation of Abeta1-42 at acidic pH and its proteolytic activity at neutral pH. Consequently, we suggest that it may be of use in the therapy of Alzheimer's disease.

Apolipoprotein E and alpha-1-antichymotrypsin polymorphisms in sporadic inclusion body myositis

Sporadic inclusion body myositis (s-IBM) is a progressive muscle disease of unknown aetiology. Characteristically, intracellular amyloid deposits are detectable, including beta-amyloid precursor protein, phosphorylated tau, alpha1-antichymotrypsin (alpha1-ACT) and apolipoprotein E (ApoE). Polymorphisms and mutations of the encoding genes have been identified in a variety of neurodegenerative diseases including Alzheimer's disease (AD). Beside other factors, polymorphisms may lead to protein accumulation in both diseases. In particular, polymorphisms within the ApoE and alpha1-ACT gene have been implicated in the aetiology of AD and s-IBM. We analysed ApoE and alpha1-ACT gene polymorphisms in 35 s-IBM patients. We could not identify any statistical significant correlation between distinct ApoE and alpha1-ACT genotypes and the risk of developing s-IBM. Additionally, ApoE and alpha1-ACT genotypes seem not to influence the onset age of s-IBM. A combination of different alpha1-ACT and ApoE genotypes appears not to enhance the risk of developing s-IBM. Therefore, allelic variations of alpha1-ACT and ApoE are unlikely to be genetic key factors in the aetiology of s-IBM.

Plasma and cerebrospinal fluid alpha1-antichymotrypsin levels in Alzheimer's disease: correlation with cognitive impairment

alpha-1-Antichymotrypsin (ACT) is present in neuritic plaques in which it participates in the inflammatory cascade of Alzheimer's disease (AD). Reports of blood ACT levels in AD, and its usefulness as a disease biomarker, have been conflicting. In an effort to clarify this, we measured plasma ACT levels in 516 white subjects including 359 subjects with probable or possible AD, 44 subjects with other late-life dementias, and 113 nondemented people. Subjects with systemic inflammatory diseases or who were taking antiinflammatory medications were excluded. All patients underwent extensive medical and detailed neuropsychological examinations at the time their blood was drawn. We found that plasma ACT levels were elevated in AD patients compared with the control group (p = 0.01) and were associated with severity of AD dementia; there was a negative association with the Mattis Dementia Rating Scale (a global measure of cognition) and a positive association with the Clinical Dementia Rating Scale (a global functional assessment). These relationships remained significant after controlling for demographic and genetic variables. When AD subjects were stratified into subgroups by dementia severity, matched by age, education, and gender, increased serum ACT correlated with Clinical Dementia Rating Scale (p = 0.0041) or Mattis Dementia Rating Scale (p = 0.0031) scores. ACT measurements in cerebrospinal fluid from an additional 34 AD cases and 16 controls showed elevated levels (p = 0.02) in AD. There was a negative correlation (p = 0.037) between cerebrospinal fluid ACT levels and clinical severity as measured by the Mini-Mental State Examination. Our results demonstrate that peripheral ACT levels are elevated in AD, but not in dementias other than AD, and they increase with progression of AD dementia. Although not useful as a diagnostic biomarker, ACT may reflect disease severity and may be helpful as a within subject biomarker in interventions (particularly with antiinflammatory agents) directed at slowing or halting progression of disease.

Alpha2-macroglobulin deletion polymorphism and plasma levels in late onset Alzheimer's disease

The acute-phase "panproteinase" inhibitor alpha2-macroglobulin (alpha2M), a protein involved in inflammatory reactions, has been identified in amyloid plaques in Alzheimer's disease (AD). In addition, alpha2M is involved in AD susceptibility at the genetic level, and a deletion polymorphism at the a2M gene has been found to be associated with sporadic AD. We analyzed the deletion polymorphism and alpha2M plasma levels in 93 ultraoctuagenarian patients with late-onset sporadic AD and in controls (n=157). alpha2M allele frequencies did not differ between AD patients (alpha2M*2=0.169) and controls (alpha2M*2=0.146). The mean plasma concentrations of alpha2M were similar in patients (271.8+/-79 mg/dl) and controls (269.5+/-81.2 mg/dl). No difference was found in the alpha2M mean plasma levels associated with the three alpha2M genotypes, indicating that the deletion has no effect on alpha2M protein level. However, in AD patients alpha2M mean plasma values differed significantly according to apolipoprotein E genotypes (p=0.03), with E3/E3 homozygotes showing the highest levels. Since in a previous work E3/E3 were found to be associated with the highest plasma levels of alpha1-antichymotrypsin, another acute-phase protein, the present findings seem to support the hypothesis that inflammation may be a relevant factor in AD pathogenesis peculiar to E3/E3 subjects.

Plasma α1-antichymotrypsin in Alzheimer’s disease; relationships with APOE genotypes

Inflammatory processes are thought to be important contributors to the pathogenesis of Alzheimer's disease (AD). alpha1-antichymotrypsin (ACT) is a proteinase inhibitor characteristic of acute-phase inflammation and has been identified in amyloid plaques. We analyzed the plasma ACT levels in a sample of subjects with late-onset AD and correspondent controls. Plasma ACT was higher in AD patients (62.8 +/- 20.2 mg/dl) than in controls (58.8 +/- 18.1 mg/dl), but not significantly (P = 0.13). In the AD patients regression analysis showed a positive linear relationship between ACT levels and duration of the disease (P = 0.037). Increased ACT concentrations (64.6 +/- 21.2 mg/dl) were also found in patients with greater cognitive impairment (MMSE scores < 20), but since this factor depends on the duration of the disease as well, our present data seem to indicate a complex relationship involving elevated ACT levels, disease duration and cognitive impairment. Plasma ACT was found to differ significantly according to APOE genotypes (P = 0.017), the highest levels being associated to E3-E3 homozygotes (66.1 +/- 17.8 mg/dl) and the lowest to E4-E3 subjects (53.1 +/- 18.2 mg/dl). In patients not carrying APOE*4 allele the ACT levels were higher than in controls (P = 0.014), and the relationship between ACT and disease duration was stronger than that observed in the total AD sample (P = 0.003), but it was absent in those carrying APOE*4 (P = 0.67). Taken together our results seem to suggest that inflammation is a relevant factor in AD pathogenesis for subjects with E3-E3 and E3-E2 genotypes but less important for APOE*4 carrying subjects.

Central beta-amyloid peptide-induced peripheral interleukin-6 responses in mice

beta-Amyloid peptides (Abetas) share with lipopolysaccharide, a potent pro-inflammatory agent, the property of stimulating glial cells or macrophages to induce various inflammatory mediators. We recently reported that central administration of lipopolysaccharide induces peripheral interleukin-6 responses via both the central and peripheral norepinephrine system. In this study, the effect of intracerebroventricular injection of various synthetic Abetas on plasma interleukin-6 levels was examined in mice. Abeta(1-42) dose-dependently increased plasma interleukin-6 levels: 'aged' Abeta(1-42) was more effective than fresh, whereas Abeta(42-1) had no effect. 'Aged' Abeta(1-42) (205 pmol/mouse i.c.v.)-induced plasma interleukin-6 peaked at 2 h post injection, which is earlier than the peak time of the Abeta(1-42)-induced brain interleukin-6, tumor necrosis factor-alpha and interleukin-1beta levels, which was 4, 4 and 24 h, respectively. Among various peripheral organs, Abeta(1-42) (205 pmol/mouse i.c.v.) significantly increased interleukin-6 mRNA expression in lymph nodes and liver. Abeta(1-42) (205 pmol/mouse i.c.v.) significantly increased norepinephrine turnover in both hypothalamus and spleen. Either central or peripheral norepinephrine depletion effectively inhibited the Abeta(1-42)-induced peripheral interleukin-6 response. Pretreatment with prazosin (alpha(1)-adrenergic antagonist), yohimbine (alpha(2)-adrenergic antagonist), and ICI-118,551 (beta(2)-adrenergic antagonist), but not with betaxolol (beta(1)-adrenergic antagonist), inhibited Abeta(1-42)-induced plasma interleukin-6 levels. These results demonstrate that centrally administered Abeta(1-42) effectively induces the systemic interleukin-6 response which is mediated, in part, by central Abeta(1-42)-induced activation of the central and the peripheral norepinephrine systems.

Epidemiology of dementia: concepts and overview

This article reviews current knowledge about the prevalence and incidence of dementia and the risk and protective factors for dementia. Relevant epidemiologic concepts and methodological issues are reviewed, focusing on the implications of designing and interpreting epidemiologic studies of dementia and illustrating the integrative role of epidemiology.

Elevated plasma neopterin levels in Alzheimer disease

We assessed plasma neopterin level as a marker of inflammation in Alzheimer disease (AD). Plasma neopterin levels were higher in 51 patients with AD (9.3 +/- 5.9 ng/mL) than in 38 age-matched control subjects (6.3 +/- 2.6 ng/ml, p = 0.002). There was no correlation between neopterin levels and Mini-Mental State Examination score or duration of disease; there was a weak association between neopterin level and age (r = 0.26, p = 0.02). Although measurement of plasma neopterin levels is not useful for diagnosis, this assay may provide guidance for the development of anti-inflammatory treatment strategies for AD.

Association of serum AACT levels and AACT signal polymorphism with late-onset Alzheimer's disease in Northern Ireland

alpha1-antichymotrypsin (AACT) is a serine protease inhibitor that has been associated with amyloid plaques in the brains of patients with Alzheimer's disease (AD). It has been reported that AACT serum levels are higher in AD patients than in age and sex matched controls. In addition, polymorphisms in the signal peptide and 5' of the AACT gene have been reported to increase the risk of developing AD. Serum AACT has also been suggested to be associated with cognitive decline in elderly subjects. Our objective was to investigate whether a relationship existed between serum AACT levels, AACT genotypes and risk for AD in a case control association study using 108 clinically well defined late onset AD cases and 108 age and sex matched controls from Northern Ireland. We also wished to determine whether higher serum AACT affected levels of cognition as had been previously reported. Serum AACT levels were found to be significantly raised in cases compared to controls (t=3.8, df=209, p<0.001). However, we detected no relationship between serum AACT levels and cognitive decline. We report allelic association of the AACT signal polymorphism with AD (chi(2)=3.70, df=1, p=0.04) but we failed to show any correlation between AACT serum levels and genotype.

Indications for shunting in patients with idiopathic normal pressure hydrocephalus presenting with dementia and brain atrophy (atypical idiopathic normal pressure hydrocephalus)

The indications for shunt operation in patients with idiopathic normal pressure hydrocephalus accompanied by brain atrophy (atypical idiopathic normal pressure hydrocephalus: AINPH) were investigated in 25 patients who satisfied the diagnostic criteria and underwent ventriculoperitoneal (VP) shunting. All patients had no apparent history of intra- or extracranial disease; dementia and gait disturbance as the main complaints; moderate to severe cerebral atrophy and ventricular dilatation and at least periventricular low density around the anterior horn on computed tomography; normal cerebrospinal fluid (CSF) pressure and filling of ventricles or cortical surface space with contrast medium at 24 hours on cisternography. The 15 male and 10 female patients were aged 47-83 years (mean 60.4 years). VP shunting was effective in 12 improved patients and not effective in 13 unimproved patients according to NPH grading. Pathological pressure wave on epidural pressure monitoring was observed in eight of 12 improved patients, but none of 13 unimproved patients. CSF outflow resistance was 35.33 +/- 11.16 mmHg/ml/min in improved patients and 9.12 +/- 3.51 mmHg/ml/min in unimproved patients. Preoperative serum alpha-1-antichymotrypsin value (alpha-1-ACT) was 42.02 +/- 8.64 mg/dl in improved patients and 61.72 +/- 11.03 mg/dl in unimproved patients. Alpha-1-ACT over 55 mg/dl occurred only in unimproved patients. Cerebral arteriovenous difference of oxygen content value (c-AVDO2) before and after surgery was 6.34 +/- 0.9 ml% and 5.91 +/- 0.78 ml% in improved patients and 4.75 +/- 1.85 ml% and 4.81 +/- 1.73 ml% in unimproved patients, respectively. The two cases with preoperative c-AVDO2 value over 8.5 ml% were both unimproved. Mean cerebral blood flow value before and after surgery was 23.51 +/- 4.20 ml/100 g/min and 45.22 +/- 8.11 ml/100 g/min in improved patients and 21.77 +/- 5.12 ml/100 g/min and 24.82 +/- 4.97 ml/100 g/min in unimproved patients, respectively. Cerebral atrophy in improved patients is caused by a cerebral circulation disturbance defined as a cerebral blood flow of penumbra or more due to cerebral arteriosclerosis, etc. A flow-chart of indications of shunt surgery for AINPH was prepared based on the results of the present study.

Blood levels of alpha-1-antichymotrypsin and risk factors for Alzheimer's disease: effects of gender and apolipoprotein E genotype

Concentrations of alpha(1)-antichymotrypsin (ACT) were measured in serum or plasma samples from 137 patients with late-onset probable Alzheimer's disease (AD) and 89 controls. Levels of ACT from sera or plasma from both AD or controls were different, being highest in serum samples. Increased levels of serum or plasma ACT and normal levels of C-reactive protein (CRP) were found in AD. Differences in serum ACT levels between AD and controls were statistically significant, while those in plasma ACT were not. ACT serum levels were higher in women with AD that in female and male controls. Apolipoprotein E (APOE) genotypes did not independently affect blood ACT levels in both AD and controls; although, among AD patients, female AD patients with APOE 4,4 showed the highest level of serum ACT. The gender effect appeared to be prominent, since female AD patients with APOE 3,3 had similar ACT levels to those of female AD patients with APOE 4,4.

The non-steroidal anti-inflammatory drug tepoxalin inhibits interleukin-6 and alpha1-anti-chymotrypsin synthesis in astrocytes by preventing degradation of IkappaB-alpha

Tepoxalin is a structurally and functionally novel non-steroidal anti-inflammatory drug (NSAID) with potent anti-inflammatory and analgesic properties. Apart from its inhibitory effect on cyclooxygenase activity, tepoxalin is able to inhibit production of cytokines in peripheral cells outside the CNS. No data, however, are available concerning the effects of this drug in the CNS. Since cytokines such as interleukin-1 (IL-1) or interleukin-6 (IL-6) as well as acute-phase proteins such as alpha1-anti-chymotrypsin (ACT) participate in the etiopathology of Alzheimer's disease (AD), we were interested whether tepoxalin is able to inhibit the synthesis of these immunomodulators in primary rat microglia and astrocytes as well as in the human astrocytoma cell line U373 MG. We found that tepoxalin markedly inhibits IL-1beta-induced IL-6 and ACT synthesis in astrocytes and the synthesis of IL-1beta and IL-6 in lipopolysaccharide (LPS)-stimulated microglial cells. Electrophoretic mobility shift and reporter gene assays revealed that tepoxalin exerts its inhibitory effect through the inhibition of nuclear factor kappaB (NF-kappaB), a transcription factor involved in the induction of IL-1, IL-6 and ACT gene expression. We show that inhibition of NF-kappaB activation by tepoxalin is mediated by preventing IkappaB-alpha degradation. Based on this inhibitory effect of tepoxalin on cytokine and ACT synthesis and the documented therapeutic efficacy of NSAIDs in AD, we conclude that tepoxalin may be of therapeutic benefit for the treatment of AD patients and should therefore be tested in clinical trials.

Inflammation and Alzheimer's disease: relationships between pathogenic mechanisms and clinical expression

During the past 15 years a variety of inflammatory proteins has been identified in the brains of patients with Alzheimer's disease (AD) postmortem. There is now considerable evidence that in AD the deposition of amyloid-beta (A beta) protein precedes a cascade of events that ultimately leads to a local "brain inflammatory response." Here we reviewed the evidence (i) that inflammatory mechanisms can be a part of the relevant etiological factors for AD in patients with head trauma, ischemia, and Down's syndrome; (ii) that in cerebral A beta disorders the clinical symptoms are determined to a great extent by the site of inflammation; and (iii) that a brain inflammatory response can explain some poorly understood characteristics of the clinical picture, among others the susceptibility of AD patients to delirium. The present data indicate that inflammatory processes in the brain contribute to the etiology, the pathogenesis, and the clinical expression of AD.

Serpins inhibit the toxicity of amyloid peptides

The amyloid plaque in Alzheimer's disease (AD) contains numerous proteins, some of which may be relevant to the pathogenesis of the disease. The serine protease inhibitor alpha1-antichymotrypsin is specifically localized in AD plaques. It is shown here that alpha1-antichymotrypsin and several other serine protease inhibitors (serpins) inhibit the toxicity of amyloid peptides on primary cortical nerve cell cultures as well as a clonal cell line. This inhibition of toxicity is not mediated via the serpin enzyme complex receptor, the transferrin receptor, or by interference with the polymerization of amyloid fibrils. Since a variety of synthetic serine protease inhibitors mimic the effects of serpins on amyloid toxicity, it is likely that the antiprotease activities of serpins are responsible for their biological effects.

Apolipoprotein E and alpha1-antichymotrypsin polymorphism in Alzheimer's disease

A recent observation has shown that a common polymorphism in the alpha1-antichymotrypsin (ACT) gene modifies the apolipoprotein E (ApoE) epsilon4-associated Alzheimer's disease (AD) risk identifying the combination of the ACT/AA and ApoE epsilon4/epsilon4 genotypes as a potential susceptibility marker for AD. We analyzed the segregation of the ApoE and ACT polymorphism in sporadic and familial AD patients. In none of the sporadic AD patients did we find the combination of the ACT/AA and ApoE epsilon4/epsilon4 genotypes. The frequency of ApoE epsilon4/epsilon4 homozygosity in the AD sample resulted highest for the ACT/ TT genotype (17.6%). Our data fail to confirm any additional association with AD beyond the ApoE epsilon4 allele with any ACT genotype, suggesting that ACT does not represent an additional risk factor for AD.

Inflammation and Alzheimer disease

Inflammatory mechanisms are active in patients with Alzheimer disease. Serum elevations of acute phase proteins such as alpha 1-antichymotrypsin, along with deposition of inflammatory cytokines in the brain, suggest a "cerebral acute phase response" contributing to amyloid deposition and tissue destruction. Activated microglia possessing HLA-DR surface markers accumulate around amyloid plaques. The complement cascade leads to generation of the membrane attack complex, which may directly damage neuronal membranes. This growing body of evidence suggests that empirical trials of anti-inflammatory drugs are now appropriate to test the hypothesis that suppression of these mechanisms will slow the rate of progression of Alzheimer disease. Several drugs useful in the treatment of rheumatic diseases are candidates for study in Alzheimer disease, including glucocorticoids, antimalarial drugs, and colchicine. Pilot studies of the synthetic glucocorticoid prednisone indicate that treatment with a moderate dose is well tolerated in patients with Alzheimer disease, and suppresses serum levels of acute phase proteins. Based on this experience, a multicenter parallel-design placebo-controlled trial has been initiated with Alzheimer's Disease Cooperative Study to determine whether treatment with prednisone can slow the rate of progression of Alzheimer disease.

Serum alpha 1-antichymotrypsin level as a marker for Alzheimer-type dementia

Excessive alpha 1-antichymotrypsin (ACT) in brain has been postulated to play a role in the pathogenesis of Alzheimer's disease (AD). We measured serum ACT by radial immunodiffusion in 57 patients with presumed AD, 110 healthy controls (24 children; 86 adults), 67 non-AD patients from a geriatric private practice and a VA nursing home, and 136 asthmatics (56 adults; 80 children) as an inflammatory disease control group. Serum ACT was significantly higher in AD (73.1 +/- 22 mg/dl) than in healthy controls (47.9 +/- 8.1 mg/dl) or non-AD patients (61.8 +/- 23.9 mg/dl). A level of 60 mg/dl best separated AD patients from controls or non-AD patients. Serial measurements served to distinguish elevations of ACT level in AD from non-AD inflammatory conditions; the ACT level in the latter returned to normal with therapy or time, but the levels in AD remained elevated. A measure of serum ACT by radial immunodiffusion can be used to support a diagnosis of AD disease but not necessarily as a screening test due to the potentially large number of false positives (26% in the population studied) should malignancy or inflammatory disease be concurrent.

Trypsin inhibition: a potential cause of cobalamin deficiency common to the pathogenesis of Alzheimer-type dementia and AIDS dementia complex?

There is increasing evidence for an association between Alzheimer-type dementia (AD) and nutritionally independent cobalamin deficiency. Furthermore, low serum cobalamin values occur in a kindred with familial Alzheimer's disease (FAD) and histopathological confirmation of AD neuropathology. The Cobalamin deficiency could be either a consequence or cause of amyloidogenesis. Cobalamin deficiency is also associated with the acquired immunodeficiency syndrome (AIDS). A common pathogenic mechanism may exist for AIDS dementia complex (ADC) and AD, but there is no explanation at present for these associations. This paper presents the hypothesis that protease inhibition is a common factor in AD and ADC resulting in protein-bound cobalamin malabsorption and disrupted cobalamin metabolism.