David L. Marcus

Increased Peroxidation and Reduced Antioxidant Enzyme Activity in Alzheimer's Disease☆

The overall peroxidation activity in brain tissue by region from patients with Alzheimers disease (AD) and age-matched controls was determined employing the thiobarbituric acid-reactive substances (TBARS) assay, a measure of lipid peroxidation, followed by a determination the activities of the antioxidant enzymes Cu/Zn superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT), in the frontal, temporal, and cerebellar cortex of 10 AD and 9 control brains. The level of TBARS was elevated in all regions, with particular statistical significance in the temporal cortex when compared to age-matched controls. SOD activity was significantly decreased in AD frontal and AD temporal cortex, while catalase activity was significantly decreased in AD temporal cortex. There was no significant difference in GSH-Px activity found in any of the regions examined. This study supports the theory that in AD the brain is affected by increased oxidative stress which, when combined with a decrease in SOD activity, produces oxidative alterations, seen most significantly in temporal cortex in AD, where the pathophysiologic changes are most severe.

Brain Glucose Metabolism in Alzheimer’s Disease

In vitro determination of brain glucose metabolism in the temporal cortex from patients with Alzheimers disease showed a marked decrease when compared with nondemented, age-matched control subjects. Additional determinations on normal human temporal cortex obtained at autopsy demonstrated an age-dependent decline in the rate of glucose use. These data provide an in vitro correlate for positron emission tomography studies that suggest decreased brain glucose use in Alzheimers disease.

Low Serum B12 Levels in a Hematologically Normal Elderly Subpopulation

Serum Vitamin B12 levels were determined on 378 patients ranging in age from 56 to 104 years with a median age of 77 for both males and females. A radiodilution method was employed for these determinations. This screening procedure identified 26 patients with low serum B12 levels. Nineteen of these patients had no other symptoms and were hematologically normal. The B12 binding proteins, transcobalamins (TC) I, II, and III were quantitated employing QUSO and DEAE cellulose batch separations. The total number of TC II binding/affinity sites for B12 were elevated in both the normal and low B12 elderly groups. About 17% of the total serum B12 was carried by TC II in the control group while only 4% of the total was carried on TC II in both the normal and low B12 elderly. This was accompanied by an increase in unsaturation in TC II for these two groups. The findings suggest that an alteration in the TC II‐B12 delivery system has occurred in the elderly.

Apoptotic Gene Expression in Alzheimer's Disease Hippocampal Tissue

Alzheimers disease (AD) is the major cause of dementia, accounting for 50% to 70% of the late-onset patients, with 17 to 20 million affected. It is characterized by neurofibrillary tangles, neuronal loss, and amyloid plaques in tissues of the cortex, hippocampus, and amygdala. Apoptosis or programmed cell death appears in the progression of AD. In this study, we investigated the gene expression of 14 apoptotic genes (E2F1, p21/WAF, ICE-LAP3, Fas Antigen, CPP-32, GADD153, ICE-β, c-Fos, c-Jun, Bax-α, Bcl-2, Bcl-(x)L, BAK, and p53) in 5 normal and 6 AD human hippocampal tissues, using reverse transcription-polymerase chain reaction. Our results show an upregulation of gene expression in AD patients for c-Fos and BAK. ICE-β, c-Jun, Bax-α, Bcl-x(L), p53, and GADD153 were found to be upregulated in some AD samples but were not detected or downregulated in other AD or normal samples. No gene expression was found for E2F1 , p21/WAF, ICE-LAP3, Fas Antigen, CPP32, or Bcl-2. These results indicate significant increases in c-Fos , c-Jun, and Bak; therefore, we suggest that these genes may be critical in the apoptotic cascades of AD.

Effect of cimetidine on δ-aminolevulinic acid synthase and microsomal heme oxygenase in rat liver

Cimetidine is a well known inhibitor of the heme-containing enzyme cytochrome P-450. We have found that it also inhibits delta-aminolevulinic acid synthase (ALA-S) and microsomal heme oxygenase, the rate-limiting enzymes for heme synthesis and heme degradation respectively. Cytochrome P-450 content was decreased but microsomal heme concentration remained unaltered for a period of 30 min after in vivo cimetidine administration to rats. In vitro incubation of cimetidine with each of the above enzymes revealed no direct effect of cimetidine on ALA-S but about 50% inhibition of heme oxygenase and 20% reduction in cytochrome P-450 content. This suggests that a metabolite of cimetidine inhibits ALA-S activity in vivo, while the drug itself or a metabolite inhibits heme oxygenase both in vivo and in vitro. A rise in ALA-S activity seen after its early inhibition and its return to approximate control values after 60 min suggest a reversible inhibition of ALA-S by a metabolite of cimetidine and may correspond to its clearance from the animal. An elevation in microsomal heme content paralleled the rise in ALA-S activity while microsomal heme oxygenase activity returned to only 65% of control value 60 min after cimetidine treatment. Cytochrome P-450 content did not change after its initial decrease, suggesting that irreversible alteration had occurred.

Decreased Brain Glucose Metabolism in Microvessels from Patients with Alzheimer's Disease

ABSTRACT: We studied brain glucose metabolism in patients with Alzheimers disease and age‐matched controls in vivo by PET and assessed brain glucose utilization and the phosphorylation constant K3 for hexokinase. In addition we determined in vitro the binding of 2DG and measured its phosphorylation to 2DG‐phosphate in cerebral microvessels obtained at autopsy from subjects with Alzheimers disease and age‐matched controls. In patients with Alzheimers disease we found a marked decrease in the kinetic constant K3 for the hexokinase, and a marked decrease in the overall metabolism of glucose in our PET studies; in microvessels there was a marked decrease in the affinity of 2DG and a decrease in hexokinase activity. Alzheimers disease may be related to a complex alteration in brain glucose metabolism.

Folate and Vitamin B12Levels in an Urban Elderly Population With Chronic Diseases

Folate levels of serum and red blood cells (RBC) and vitamin B12 serum levels were investigated in 326 urban chronically ill elderly ambulatory patients and 41 healthy young control subjects. Two laboratory methods were used for investigating the folate levels, the microbiologic assay (MBA) with Lactobacillus casei and radioassay (RA). Serum and RBC samples of 326 patients were tested by the folate MBA and 270 of the same samples by the RIA methods. In the MBA 6.8% of the patients and 12.2% of controls had low levels of folate RBC (less than 200 nglmL) and 1.8% of patients and 4.8% of controls had low serum folate levels (less than 5 ng/mL). All of the patients with the low folate levels had normal hematologic findings and no clinical symptoms of folate deficiency. In the RIA method, all of the patients and almost all of the control subjects (except one) had normal folate levels. Ten of the patients (3%) had low levels of serum vitamin (less than 200 pg/mL). They were hematologically normal. They had normal Schilling tests and normal vitamin B12 dietary intake. Their RBC folate levels were normal and even somewhat higher. Forty percent of these patients had macular degeneration of the eyes. The data indicate the superiority of the RA method over the MBA and bring into question the accuracy of previous studies. The data furnish further evidence that a low vitamin B12 level in the elderly is not necessarily a true vitamin B12deficiency and raise the possibility of an association between low B12 serum levels and macular degeneration of the eyes.

Anemia and the elderly: is it physiology or pathology?

There is currently a controversy of whether elderly people (over age 65) have an age-related physiologic decline in red cell parameters. If this is so, a new normal range might be established for geriatric patients, as has been suggested by others.1–6 However, since anemia is often the first sign of severe illness in a patient, new normal values might include a danger of overlooking patients with true anemia secondary to an underlying disease.7–10 In this article we shall review what is known about red cell parameters in elderly patients and attempt to answer the questions of whether new geriatric norms should be established.

Folic Acid Deficiency in the Elderly

Much has been written but little is really known about nutritional deficiencies in the elderly. In recent years we have initiated a systematic study of low folic acid levels in a geriatric population, which is one of the more common vitamin deficiencies in the United States. In this review we shall examine what is known about the series of events which may lead to a folate deficiency in the elderly. The term folic acid commonly refers to a large group of pteridine compounds, the parent compound of which is pteroylmonoglutamic acid (Figure 1). Only the reduced derivatives of folic acid serve any biologic role. All folate-dependent enzymes use only tetrahydro derivatives, with the exception of the enzyme that reduces dihydrofolic acid (DHF) to tetrahydrofolic acid (THF). The basic folate pathway is limited to the cytosol, although individual enzymes have been isolated from other organelles, including the mitochondria. Some of the important enzymes of the folate pathway include: 1) dihydrofolate reductase, the key enzyme in 1-carbon metabolism, which produces tetrahydrofolate from folic acid; 2) serine transhydroxymethylase, responsible for conversion of serine to glycine; 3) T H F methyltransferase, which catalyzes the methylation of homocysteine to methionine. This is a cobalamin (vitamin B,,)-containing enzyme that requires catalytic levels of a reducing system and S-adenosylmethionine; and 4) thymidylate synthetase, which is involved in the formation of dTMP from dUMP and, hence, DNA synthesis. Both human serum and red cells contain mainly 5-methyl THF and polyglutamates as the folate compound (Figure 2).

Iron requirement for isolated rat liver mitochondrial protein synthesis

Isolated rat liver mitochondrial protein synthesis was severly inhibited by alpha, alpha-dipyridyl (a ferrous iron-chelating agent), chloramphenicol and hemin (10(-7) M or greater). In contrast, gamma, gamma-dipyridyl (a non-iron-chelating analogue of alpha, alpha-dipyridyl), cycloheximide and lower concentrations of hemin were non-inhibitory. The inhibitory action of alpha, alpha-dipyridyl was reversed by addition of Fe(NH4)2(SO4)2 while ZnCl2, CuCl2 and CoCl2 were ineffective. Hemin, however, did not protect against the alpha, alpha-dipyridyl inhibition of mitochondrial protein synthesis. These results indicate that ferrous iron is required for mitochondrial protein synthesis and suggests that it is through a mechanism independent of hemin concentration.