SENILE CEREBRAL, PANCREATIC INSULAR AND CARDIAC AMYLOIDOSIS

Amyloid Bone Disease and Highly Permeable Synthetic Membranes

The effect of different highly permeable membranes on amyloid bone disease (ABD) was retrospectively evaluated in patients on renal replacement therapy (RRT) in our Unit with a dialytic age of more than 4 years. A group of 36 patients (age 60 ± 12 years) after a variable period (28 ± 29 months) on hemodialysis with cuprophane membrane (CU-HD), were moved to HDF with a reinfusate volume of 22 ± 1 1/session, for a period of 65 ± 26 months using the following membranes: AN69 1.6 m2, PAN 1.8, PMMA 2.1, PS 1.3, polyamide (PA) 1.3 and 1.6. Bone x-rays of wrists, hips and shoulders were taken annually and the presence of ABD was evaluated according to generally accepted criteria. ABD occurred in 4 patients after a period of 73 ± 30 months on CU-HD only; it developed in 4/7 patients an AN69, in 4/6 on PAN, in 3/5 on PMMA, in 3/5 on PS; no patient of the 13 on PA developed ABD. Comparing patients on PA with those on other synthetic membranes, no significant difference was found in dialysis time (73 ± 19 vs 83 ± 28 months) as well as in age (59 ± 13 vs 61 ± 11 years) at ABD on set, when present. These data strongly encourage prospective studies enrolling more patients for a longer period of observation in order to evaluate possible differences on ABD development among various synthetic membranes.

Cognitive dysfunction and diabetes mellitus

The deleterious effects of diabetes mellitus on the retinal, renal, cardiovascular, and peripheral nervous systems are widely acknowledged. Less attention has been given to the effect of diabetes on cognitive function. Both type 1 and type 2 diabetes mellitus have been associated with reduced performance on numerous domains of cognitive function. The exact pathophysiology of cognitive dysfunction in diabetes is not completely understood, but it is likely that hyperglycemia, vascular disease, hypoglycemia, and insulin resistance play significant roles. Modalities to study the effect of diabetes on the brain have evolved over the years, including neurocognitive testing, evoked response potentials, and magnetic resonance imaging. Although much insightful research has examined cognitive dysfunction in patients with diabetes, more needs to be understood about the mechanisms and natural history of this complication in order to develop strategies for prevention and treatment.

Cognitive dysfunction and diabetes mellitus

The deleterious effects of diabetes mellitus on the retinal, renal, cardiovascular, and peripheral nervous systems are widely acknowledged. Less attention has been given to the effect of diabetes on cognitive function. Both type 1 and type 2 diabetes mellitus have been associated with reduced performance on numerous domains of cognitive function. The exact pathophysiology of cognitive dysfunction in diabetes is not completely understood, but it is likely that hyperglycemia, vascular disease, hypoglycemia, and insulin resistance play significant roles. Modalities to study the effect of diabetes on the brain have evolved over the years, including neurocognitive testing, evoked response potentials, and magnetic resonance imaging. Although much insightful research has examined cognitive dysfunction in patients with diabetes, more needs to be understood about the mechanisms and natural history of this complication in order to develop strategies for prevention and treatment.

Increased risk of type 2 diabetes in Alzheimer disease

Alzheimer disease and type 2 diabetes are characterized by increased prevalence with aging, a genetic predisposition, and comparable pathological features in the islet and brain (amyloid derived from amyloid beta protein in the brain in Alzheimer disease and islet amyloid derived from islet amyloid polypeptide in the pancreas in type 2 diabetes). Evidence is growing to link precursors of amyloid deposition in the brain and pancreas with the pathogenesis of Alzheimer disease and type 2 diabetes, respectively. Given these similarities, we questioned whether there may be a common underlying mechanism predisposing to islet and cerebral amyloid. To address this, we first examined the prevalence of type 2 diabetes in a community-based controlled study, the Mayo Clinic Alzheimer Disease Patient Registry (ADPR), which follows patients with Alzheimer disease versus control subjects without Alzheimer disease. In addition to this clinical study, we performed a pathological study of autopsy cases from this same community to determine whether there is an increased prevalence of islet amyloid in patients with Alzheimer disease and increased prevalence of cerebral amyloid in patients with type 2 diabetes. Patients who were enrolled in the ADPR (Alzheimer disease n = 100, non-Alzheimer disease control subjects n = 138) were classified according to fasting glucose concentration (FPG) as nondiabetic (FPG <110 mg/dl), impaired fasting glucose (IFG, FPG 110-125 mg/dl), and type 2 diabetes (FPG >126 mg/dl). The mean slope of FPG over 10 years in each case was also compared between Alzheimer disease and non-Alzheimer disease control subjects. Pancreas and brain were examined from autopsy specimens obtained from 105 humans (first, 28 cases of Alzheimer disease disease vs. 21 non-Alzheimer disease control subjects and, second, 35 subjects with type 2 diabetes vs. 21 non-type 2 diabetes control subjects) for the presence of islet and brain amyloid. Both type 2 diabetes (35% vs. 18%; P < 0.05) and IFG (46% vs. 24%; P < 0.01) were more prevalent in Alzheimer disease versus non-Alzheimer disease control subjects, so 81% of cases of Alzheimer disease had either type 2 diabetes or IFG. The slope of increase of FPG with age over 10 years was also greater in Alzheimer disease than non-Alzheimer disease control subjects (P < 0.01). Islet amyloid was more frequent (P < 0.05) and extensive (P < 0.05) in patients with Alzheimer disease than in non-Alzheimer disease control subjects. However, diffuse and neuritic plaques were not more common in type 2 diabetes than in control subjects. In cases of type 2 diabetes when they were present, the duration of type 2 diabetes correlated with the density of diffuse (P < 0.001) and neuritic plaques (P < 0.01). In this community cohort from southeast Minnesota, type 2 diabetes and IFG are more common in patients with Alzheimer disease than in control subjects, as is the pathological hallmark of type 2 diabetes, islet amyloid. However, there was no increase in brain plaque formation in cases of type 2 diabetes, although when it was present, it correlated in extent with duration of diabetes. These data support the hypothesis that patients with Alzheimer disease are more vulnerable to type 2 diabetes and the possibility of linkage between the processes responsible for loss of brain cells and beta-cells in these diseases.

Effect of dialysis membrane and patient's age on signs of dialysis-related amyloidosis. The Working Party on Dialysis Amyloidosis

This 12 center study was designed to assess factors affecting the development and progression of beta 2-microglobulin amyloidosis in long-term dialysis. A total of 221 patients who were on hemodialysis for more than five years, and who were treated the entire time only with AN69, a biocompatible, highly permeable membrane, or cuprophane, a less permeable, poorly biocompatible membrane (Cell) were evaluated for time on dialysis, development of carpal tunnel syndrome, and cystic bone lesions. X-ray documentation was taken in a minimum of four of the six following joints: both hips, wrists and shoulders. The data demonstrate that patients treated solely by AN69 membranes display signs of bone amyloidosis less frequently than do those treated by Cell membranes. Age at onset of dialysis was found to have a striking correlation with the development of carpal tunnel syndrome and bone amyloidosis, while no significant influence was found for hyperparathyroidism, sex or year of first dialysis.

Hereditary cystatin C (gamma-trace) amyloid angiopathy of the CNS causing cerebral hemorrhage

Hereditary CNS amyloid angiopathy occurring in Icelanders is the first human disorder known to be caused by deposition of cystatin C amyloid fibrils in the walls of the brain arteries leading to single or or multiple strokes with fatal outcome. One or more affected members have been verified by histological examination in 8 families containing 127 affected. These originated from the same geographic area. Abnormally low value of cystatin C found in the cerebrospinal fluid of those affected can be used to support or make diagnosis of this disease, also in asymptomatic relatives. By amino acid sequence analysis the amyloid fibrils in the patients are found to be a variant of cystatin C (gamma-trace), a major cysteine proteinase inhibitor. The variant protein has an amino acid substitution (glutamine for leucine) at position 58 in the amyloid molecule. It is postulated that a point mutation has occurred leading to production of amyloidogenic protein causing the disorder.

Pathological Society of Great Britain and Ireland. 154th meeting, 7-9 January 1987. Synopses of papers

The transformation of serum proteins into Congo red-sensitive fibrillar material is requisite for the onset and progression of amyloid disease. All the mechanisms which lead to the disease itself have not been elucidated, but our knowledge has increased significantly. It is apparent that in all types of amyloid fibrils, three common features are displayed by the major protein constituents. These are that the fibril protein has a serum precursor, a high degree of anti-parallel beta-sheet conformation and a distinctive ultrastructure on electron microscopy. In the AL and AA forms of amyloidosis, the putative precursors appear to undergo limited degradation to form the protein component of amyloid fibrils. It has been suggested that there may be certain primary structural characteristics inherent in precursor molecules which make them amyloidogenic, thus predisposing them to amyloid fibril formation. This would include certain subtypes of immunoglobulin light chains, possibly kappa I and lambda VI, in the AL type of amyloidosis and one of the polymorphic SAA species, SAA2, which has been identified as the predominating isotype found in AA amyloid fibrils. In AH amyloidosis, the mechanism of amyloid fibril formation appears to be simply a concentration phenomenon where elevated concentrations of B2-M are not handled normally and amyloid deposition is the result. Amyloidogenesis in the hereditary form of systemic amyloidosis may involve other factors in addition to the presence of a variant precursor prealbumin as indicated by the delayed onset of the disease. It is evident that the elucidation of the mechanism(s) which governs the onset and progression of the amyloidoses will allow future regulation and treatment of these all too often complex disorders.

Cerebral amyloid angiopathy causing intracranial hemorrhage

Ten cases of sporadic cerebral amyloid angiopathy (CAA) were seen as intracranial hemorrhage. CAA was seen as a stroke or catastrophic intracranial hemorrhage in all cases. CAA complicated by intracranial hemorrhage carried a high mortality; 9 of 10 patients died in spite of aggressive medical or surgical treatment. Senile dementia of Alzheimer's type was an associated finding in only 1 patient. Computed tomographic scanning in 4 patients initially was not diagnostic for hemorrhage. Lambda chains and amyloid P protein were demonstrated in the areas of amyloid angiopathy immunocytochemically. The pathogenesis of hemorrhage in CAA could be either increased fragility of amyloid-laden blood vessels or rupture of microaneurysms. Surgical treatment of intracranial hemorrhage in CAA should therefore be undertaken with caution.

Amyloid fibril in hereditary cerebral hemorrhage with amyloidosis (HCHWA) is related to the gastroentero-pancreatic neuroendocrine protein, gamma trace

Amyloid fibrils were isolated from the leptomeningeal blood vessels obtained at autopsy from three Icelandic patients dying of Hereditary Cerebral Hemorrhage with Amyloidosis (HCHWA) and verified by Congo red staining and electron microscopy. Gel filtration on Sephadex and Ultrogel columns yielded predominantly one component (molecular weight 11,500 daltons) and also another minor component (molecular weight 15,800 daltons). Automated amino terminal sequencing showed these proteins to be similar (36 residues) to a recently described human protein, gamma trace, beginning at its eleventh amino terminal residue. The amyloid deposits in all three patients stained with rabbit anti-gamma trace antiserum. Although the function of gamma trace is not known, it appears to have structural homology with several hormones and has been localized to the brain, pancreas and pituitary. The amyloid fibril subunits seem to have polymerized after cleavage of the amino terminal decapeptide from gamma trace-related proteins. Therefore, HCHWA appears to be the first genetically determined disease related to the gastroenteropancreatic neuroendocrine system.

Senile amyloidosis: principles of localization in a heterogeneous form of amyloidosis

In order to identify amyloid deposits in patients over 60 years of age (so-called senile amyloid), the following five tissues were investigated under the light and electron microscope: 1. pituitary gland, 2. pancreatic islets of Langerhans, 3. heart, 4. aorta, and 5. brain. In all an increasing incidence of amyloid deposits was found with increasing age, and in the brain a significant quantitative increase in amyloid deposits with increasing age was observed. Despite the biochemical heterogeneity of amyloid found in old age, all the deposits seen in tissues examined were morphologically similar. Typical amyloid fibrils were always found (diameter 60-100 A), and these were invariably deposited extracellularly and primarily on basement membranes. The amyloid-binding basement membranes were in most cases those of myocytic, but were also those of endothelial or epithelial cells. The almost invariable involvement of blood vessels, indicates the importance of these structures in the genesis of the various forms of senile amyloid.

Cerebral amyloid angiopathy

Cerebral amyloid angiopathy is nonspecific disease entity that has been associated with a number of neuropathologic conditions, the most prominent being dementia and cerebral hemorrhage. It occurs more commonly than is generally appreciated, with implications that may be overlooked. Amyloid deposits are found in the vessels of the leptomeninges and cerebral cortex. There is often a close topographic relation to senile plaques, the histologic abnormality characteristic of Alzheimer's disease and senile dementia. Because of this relation and the well documented presence of amyloid in senile plaques, a similar natural history has been postulated for each. Histochemical studies indicate, however, that there are distinct differences between the amyloid deposits in cerebral vessels and senile plaques. An association between cerebral amyloid angiopathy and other forms of amyloidosis has similarly failed to be established, and a successful form of therapy has yet to be devised.

Digoxin sensitivity in amyloid cardiomyopathy

Digoxin (5 mg/ml) was added to 10-mg and 20-mg pellets of purified primary and secondary amyloid fibrils, a normal human liver and heart homogenate and a homogenate from the heart of a patient with amyloid cardiomyopathy who had not received digitalis. After centrifugation, the supernatants were recovered and assayed for digoxin concentrations. Aliquots from the sediments were studied for the presence of digoxin, using rabbits antidigoxin antiserum and an indirect immunofluorescent technique. The results showed that 0.11--0.13 ng/ml of digoxin bound per milligram of fibrils and could not be separated by repeated washings. Elution with citrate or changes in the pH of the buffer. Immunofluorescent studies demonstrated diffusely bright immunofluorescence with the fibril preparation and amyloid heart homogenate when reacted with digoxin and digoxin-specific antiserum. These studies demonstrate that isolated amyloid fibrils bind digoxin and suggest that this interaction may play some role in the sensitivity to digitalis that has been observed in some patients with amyloid cardiomyopathy.

Amyloid in normal and pathological parathyroid glands

Two groups of parathyroid glands have been examined for intrafollicular amyloid. In glands removed surgically it was found in nine cases (16%); in glands removed at necropsy it was found in 23 cases (46%). Also, two postmortem cases of systemic amyloidosis showed involvement of parathyroid glands with an entirely different distribution of amyloid. Compared with other amyloids the tinctorial properties of the intrafollicular amyloid were uniform in reactions with Congo red and Thioflavin T, but the intensity of the staining reaction for amino acids tryptophan and tyrosine was not constant for the follicle amyloid. This variation may be a feature of a maturation process but the derivation of this amyloid remains uncertain.

A n evaluation of current methods for the diagnostic histochemistry of amyloid

Six current histological methods for demonstrating amyloid (crystal violet, thioflavine-T fluorescence, Congo-red staining and fluorescence, Sirius-red staining, and Congo- or Sirius-red birefringence) were applied in 25 cases of amyloidosis of various types and 47 pseudo-amyloid lesions. The results were compared and were correlated with those of ancillary histochemical tests and clinico-pathological data and each method's sensitivity and specificity for amyloid was evaluated. Thioflavine-T and, to a lesser degree, Congo-red fluorescence and Sirius-red staining proved very sensitive but not specific. Green birefringence with Congo or Sirius red was specific but not completely sensitive. The coexistence of Congo-red (and Sirius-red) staining and a positive DMAB-nitrite reaction occurred in all amyloid specimens and appeared specific for amyloid.