Transthyretin amyloid deposits in lumbar spinal stenosis and assessment of signs of systemic amyloidosis

BACKGROUND

Wild-type transthyretin (ATTRwt) amyloidosis is the most common systemic amyloidosis in Western countries and manifests mainly as progressive restrictive cardiomyopathy.

OBJECTIVE

To study the prevalence of ATTR deposits in ligament tissue in patients undergoing surgery for lumbar spinal stenosis and to assess whether these deposits are associated with cardiac amyloidosis.

MATERIALS AND METHODS

A total of 250 patients, aged 50-89 (57% women), none with known cardiovascular disease, were included. Ligaments were investigated microscopically for amyloid. ATTR type was determined by immunohistochemistry and fibril type by Western blot. The amount of amyloid was graded 0-4. All patients with grade 3-4 ATTR deposits were offered cardiac investigation including ECG, cardiac ultrasound, plasma NT-proBNP and cardiac magnetic resonance (CMR), including modern tissue characterization.

RESULTS

Amyloid was identified in 221 of the samples (88.4%). ATTR appeared in 93 samples (37%) of whom 42 (17 women and 25 men) were graded 3-4; all had fibril type A (mixture of full-length TTR and fragmented TTR). Twenty-nine of 42 patients with grade 3-4 ATTR deposits accepted cardiovascular investigations; none of them had definite signs of cardiac amyloidosis, but five men had a history of carpal tunnel syndrome.

CONCLUSIONS

The prevalence of ATTR deposits in ligamentum flavum in patients with lumbar spinal stenosis was high but not associated with manifest ATTR cardiac amyloidosis. However, the findings of fibril type A, the prevalence of previous carpal tunnel syndrome and ATTR amyloid in surrounding adipose and vascular tissue indicate that amyloid deposits in ligamentum flavum may be an early manifestation of systemic ATTR disease.

One mutation, two distinct disease variants: unravelling the impact of transthyretin amyloid fibril composition

Although hereditary transthyretin (h-ATTR) amyloidosis is a monogenetic disease, a large variation in its phenotype has been observed. The common hypothesis of amyloid fibril formation involves dissociation of the transthyretin (TTR) tetramer into monomers that after misfolding reassemble into amyloid fibrils. This notion is partly challenged by the finding of two distinct types of amyloid fibrils. One of these, type A, consists of C-terminal ATTR fragments and full-length TTR, whereas the other, type B, consists only of full-length TTR. All organs of an individual patient contain ATTR deposits of either type A or type B fibrils, and the composition in each individual remains unchanged over time. The finding of two distinct types of ATTR fibrils suggests that there are at least two different pathways in operation for ATTR fibril formation. For the most common European mutation, TTR Val30Met, ATTR fibril composition is related to the outcome of liver transplantation, which is the first successful treatment for the disease, and the penetrance of the trait. In addition, the presence of C-terminal ATTR fragments has an impact on the affinity for various tracers used for noninvasive imaging of amyloid depositions such as 99 m-technetium-diphosphono-propanodicarboxylic acid scintigraphy and positron emission tomography utilizing Pittsburgh component B, and even for the gold standard diagnostic procedure, tissue biopsy stained by Congo red and examined under polarized light. The importance of amyloid fibril composition needs to be taken into consideration when designing clinical trials of treatment modalities, and also in the evaluation of diagnostic methods such as imaging techniques.

Magnetic Resonance Imaging in Primary Amyloidosis

Twelve patients with primary amyloidosis (AL) were investigated with magnetic resonance imaging (MRI). In 9 patients an abnormal thickening of the heart walls was present and in 2 macroglossia was found at MRI. T1 was significantly increased in liver (p<0.05) and subcutaneous fat (p<0.01) while it was decreased in the spleen (p<0.05). T2 was significantly decreased (p<0.01) in the spleen in patients with amyloidosis, while it was not significantly altered in the liver or subcutaneous fat. After therapy T1 of the liver was reduced towards normal values in 4 patients. It is concluded that MRI might be a method to quantitate the amount of amyloid deposits in the tissue, and that the effect of therapy may be monitored with this technique.

Transmissible amyloid

There are around 30 human diseases associated with protein misfolding and amyloid formation, each one caused by a certain protein or peptide. Many of these diseases are lethal and together they pose an enormous burden to society. The prion protein has attracted particular interest as being shown to be the pathogenic agent in transmissible diseases such as kuru, Creutzfeldt-Jakob disease and bovine spongiform encephalopathy. Whether similar transmission could occur also in other amyloidoses such as Alzheimer's disease, Parkinson's disease and serum amyloid A amyloidosis is a matter of intense research and debate. Furthermore, it has been suggested that novel biomaterials such as artificial spider silk are potentially amyloidogenic. Here, we provide a brief introduction to amyloid, prions and other proteins involved in amyloid disease and review recent evidence for their potential transmission. We discuss the similarities and differences between amyloid and silk, as well as the potential hazards associated with protein-based biomaterials.

Alkali-degradation of amyloid: an ancient method useful for making monoclonal antibodies against amyloid fibril proteins

The systemic amyloidoses constitute a group of life-threatening disorders at which one out of about 15 different proteins have polymerized into fibrils. Prognosis and treatment varies widely and depends on the biochemical type. Determination of this has usually to be performed by immunohistochemistry which is a challenge because of lack of monospecific antibodies that can be used on formaldehyde-fixed tissue sections. We have here used an old method to create immunogenic fragments of AL-amyloid fibrils by partial degradation and solubilization with sodium hydroxide. The mouse monoclonal antibody pwlam raised against this material, labelled AL-amyloid deposits of lambda origin strongly and specifically in sections of formaldehyde-fixed and paraffin-embedded tissues.

[Amyloid centers in Europe: the EURAMY project]

The systemic amyloidoses comprise a large group of serious protein deposition diseases. Although rather rare, the disorders are spread all over the world. Increasing understanding of pathogenic mechanisms and recent hope for treatment options demand further research and development of diagnostic procedures. The European Union Framework 6 program EURAMY (http://www.EURAMY.org) is devoted to all aspects of research on systemic amyloidoses, from molecular aspects to treatment of patients.

Amyloid fibril composition is related to the phenotype of hereditary transthyretin V30M amyloidosis

Swedish familial systemic amyloidosis with polyneuropathy (FAP) depends on a mutation leading to a methionine-for-valine substitution in transthyretin. The disease appears with different clinical manifestations, including age of onset and involvement of the heart. Liver transplantation is currently the only curative treatment, but progressive cardiomyopathy may occur post-transplant. Two amyloid deposition patterns have previously been described in the heart. In one, the amyloid consists partially of transthyretin fragments and is weakly stainable by Congo red, while in the other, only full-length molecules are found and the fibrils have a strong affinity for Congo red. The present study aimed to see whether these morphological and biochemical variations have clinical implications. Subcutaneous adipose tissue biopsies were taken from 33 patients with Val30Met FAP and examined by microscopy, electrophoresis and western blot. Clinical data included age, sex, duration of disease and echocardiographic determination of the interventricular septum (IVS) thickness. It was found that fibrils composed of only full-length transthyretin were associated with early age of onset (44.8 +/- 12.9 years), no clinical cardiac involvement and a strong affinity for Congo red. In contrast, presence of transthyretin fragments in the amyloid was associated with late age of onset (67.3 +/- 7.0 years), signs of cardiac involvement and weak Congo red staining. For each individual, the same molecular type of amyloid was found in different organs. This is the first report showing that variations in clinical appearance of familial ATTR amyloidosis are associated with specific structural differences in the amyloid fibrils, and therefore may have a molecular cause. The molecular type of amyloid can be determined from a subcutaneous fat tissue biopsy.

Identification and characterization of different amyloid fibril proteins in tissue sections

Antisera specific for 4 different classes of amyloid fibril proteins, amyloid protein AA and the immunoglobulin light-chain amyloid proteins AlambdaI, AlambdaIV, and AlambdaV, were used to identify these proteins directly in tissue sections from 25 patients with amyloidosis. The specificity of these reactions was established by blocking experiments with purified amyloid fibril proteins and Bence Jones proteins of known variable subgroups. Protein AA was detected in 17 patients, including all 13 with secondary amyloidosis, 2 with primary amyloidosis and 2 with Waldenström's macroglobulinemia. Immunoglobulin light-chain proteins AlambdaI, AlambdaIV, and AlambdaV were in 3, 1, and 2 patients, respectively, all of whom had primary or myeloma/macroglobulinemia-associated amyloidosis. Antiserum specific for the amyloid-related serum protein SAA reacted with the same tissues as anti-AA and had the same pattern of staining in tissue sections.

Ageing and amyloid fibrillogenesis: lessons from apolipoprotein AI, transthyretin and islet amyloid polypeptide

The age-associated (or senile) amyloidoses encompass a heterogeneous group of systemic or localized forms of amyloidosis. In this paper we present an overview of three age-associated amyloid forms derived from transthyretin, apolipoprotein AI and islet amyloid polypeptide. Mutations in the respective genes give rise to transthyretin and apolipoprotein AI forms of familial amyloidosis while senile forms of amyloid are associated with the wild-type proteins. Different mechanisms are probably of importance in the fibrillogenesis associated with these three amyloid types. It is also possible that different amyloidogenic pathways exist for a single amyloidogenic protein. Thus, limited proteolysis may be necessary in the fibrillogenesis in senile transthyretin amyloidosis but not in most familial transthyretin amyloidoses. Other factors in the pathogenesis of amyloidosis such as local concentration, nidus formation and glycation are also discussed.

Intracellular amyloid-like deposits contain unprocessed pro-islet amyloid polypeptide (proIAPP) in beta cells of transgenic mice overexpressing the gene for human IAPP and transplanted human islets

AIMS/HYPOTHESIS

Islet amyloid is a frequent finding in the islets of Langerhans of individuals with type 2 diabetes. The main amyloid constituent is the beta cell-derived polypeptide hormone islet amyloid polypeptide (IAPP). In general, amyloid refers to an extracellular deposit of a congophilic material, but intracellular amyloid is seen in some beta cells of transgenic mice expressing the gene for human IAPP and in human islets transplanted into nude mice. The aim of this study was to immunohistochemically characterise the intracellular amyloid.

METHODS

Antisera against the N- and C-terminal processing sites of proIAPP (which were therefore specific for proIAPP), the C-terminal flanking peptide and mature IAPP were used for immunoelectron microscopy.

RESULTS

Fibrillar aggregates were seen in the halo region of the secretory granules in some beta cells in human IAPP transgenic mice. These aggregates were labelled with proIAPP-specific antisera. Also, proIAPP reactivity was more widespread in the intracellular amyloid-like aggregates in beta cells of transgenic mice than in human islet transplants, in which the intracellular amyloid-like deposits were larger, but the proIAPP labelling was restricted to small spots within the amyloid deposits.

CONCLUSIONS/INTERPRETATION

We suggest that proIAPP forms the first amyloid fibrils and that this can occur already in the secretory granules of the beta cells. The proIAPP-derived fibrils can act as seed for further amyloid formation, now made up by IAPP. The observed difference between human islet transplants and human IAPP transgenic animals may reflect differences in stages of amyloid development.

The systemic amyloidoses: clearer understanding of the molecular mechanisms offers hope for more effective therapies

Knowledge about the systemic amyloidoses has increased considerably during the last few years. This group of diseases is characterized by great biochemical variability, including at least 11 different amyloid fibril proteins and a remarkable range of clinical manifestations. With the understanding that the pathogenesis is different in the various forms of amyloidosis, it is now being increasingly accepted that an early and accurate diagnosis, including that of the underlying biochemical nature, is crucial for a successful treatment. The elucidation of the molecular mechanisms involved in amyloidogenesis is at the basis of the recent blossoming of new, innovative and more effective therapeutic approaches.

Biclonal systemic AL-amyloidosis with one glycosylated and one nonglycosylated AL-protein

The amyloid fibril protein AL was isolated from the spleen of a patient with systemic amyloidosis. Size-exclusion chromatography of the solubilized amyloid fibrils revealed a distinct, retarded asymmetric peak. The symmetrical part of the peak showed on SDS-PAGE two positive periodic acid Schiff-staining bands at 14 and 16 kDa. Staining with Coomassie Brilliant Blue revealed in addition two proteins with masses of 13 and 20 kDa. The 14 and 16 kDa bands were the strongest ones. N-Terminal analyses of the four blotted bands showed that the N-termini were the same in all cases. Elucidation of the amino acid sequence established an AL-chain of 157 residues as well as a fragment covering positions 188-207 of the constant region. Two tryptic peptides derived from the same region, positions 25-46, showed an identical sequence, except for position 34 where both alanine and threonine residues occurred. Monosaccharide compositional analysis of the threonine-containing peptide revealed an oligosaccharide in the N-glycosylation site, position 32-34. Mass analysis of the glycopeptide verified the oligosaccharide. The AL-chains belong to the kappa 3a germline gene and verifies that the glycosylated chain is a mutated form. The AL-chains differ from that of the germline in 14 positions. The J-segment is of JkappaIII and is mutated in position 106.

Enhanced in vitro production of amyloid-like fibrils from mutant (S20G) islet amyloid polypeptide

Islet amyloid polypeptide (IAPP, "amylin") is the amyloid-fibril-forming polypeptide in the islets of Langerhans associated with type 2 diabetes mellitus. A missense mutation in the IAPP gene associated with early-onset type 2 diabetes has been identified in the Japanese population. This mutation results in a glycine for serine substitution at position 20 of the mature IAPP molecule. Whether or not formation of islet amyloid with resulting destruction of islet tissue is the cause of this diabetes is yet not known. The present in vitro study was performed in order to investigate any influence of the amino acid substitution on the fibril formation capacity. Synthetic full-length wild type (IAPPwt) and mutant (IAPPS20G) as well as corresponding truncated peptides (position 18-29) were dissolved in dimethylsulfoxide (DMSO) or in 10% acetic acid at a concentration of 10 mg/mL and their fibril forming capacity was checked by Congo red staining, electron microscopy, a Congo red affinity assay and Thioflavine Tfluorometric assay. It was found that full-length and truncated IAPPS20G both formed more amyloid-like fibrils and did this faster compared to IAPPwt. The fibril morphology differed slightly between the preparations.

CONCLUSION

The amino acid substitution (S20G) is situated close to the region of the IAPP molecule implicated in the IAPP fibrillogenesis. The significantly increased formation of amyloid-like fibrils by IAPPS20G is highly interesting and may be associated with an increased islet amyloid formation in vivo and of fundamental importance in the pathogenesis of this specific form of diabetes.

Codeposition of apolipoprotein A-IV and transthyretin in senile systemic (ATTR) amyloidosis

Protein material was extracted from amyloid-rich sections of formalin-fixed and paraffin-embedded heart tissue from an individual with senile systemic amyloidosis, known to contain wild-type transthyretin as major amyloid fibril protein. Amino acid sequence analysis of tryptic peptides of this material revealed in addition to transthyretin sequences, also amino acid sequence corresponding to an N-terminal fragment of apolipoprotein A-IV. In immunohistochemistry, an antiserum to a synthetic apolipoprotein A-IV peptide labeled amyloid specifically. This peptide formed spontaneously amyloid-like fibrils in vitro and enhanced fibril formation from wild-type transthyretin. We conclude that several apolipoproteins, including apolipoprotein A-IV, may be important minor amyloid constituents, promoting fibril formation.

Chemical typing of amyloid protein contained in formalin-fixed paraffin-embedded biopsy specimens

The human amyloidoses represent a heterogeneous group of disorders characterized by the deposition of fibrillar protein in vital organs. Given the fact that at least 20 different molecules can form fibrils, the unambiguous identification of the type of amyloid deposited is critical to the correct diagnosis and treatment of patients with these disorders. Heretofore, this information has been inferred from particular clinical features of the disease, ancillary laboratory tests, and results of immunohistochemical analyses. However, to establish unequivocally the kind of protein that is deposited as amyloid, it is necessary to determine its chemical composition through amino acid sequencing or mass spectroscopy of material extracted from fibrillar deposits. We have developed a micromethod whereby such studies can be performed readily using sections of formalin-fixed, paraffin-embedded biopsy specimens. The ability to identify precisely the nature of the tissue deposits has diagnostic, therapeutic, and prognostic implications for patients with amyloid-associated disorders.

Apolipoprotein A-I-derived amyloid in atherosclerosis. Its association with plasma levels of apolipoprotein A-I and cholesterol

Wild-type apolipoprotein A-I (apo A-I)-derived amyloid commonly occurs in atherosclerotic plaques. To clarify apo A-I amyloid formation, plasma levels of apo A-I and cholesterol were related to the presence of amyloid in atherosclerotic plaques in 15 patients with peripheral atherosclerosis, subjected to arterial reconstruction. Plasma levels of apo A-I and high-density lipoprotein (HDL) cholesterol were slightly higher in patients with apo A-I-derived amyloid than in those without, but the difference was not significant. Levels of low-density lipoprotein cholesterol and total cholesterol were significantly higher in the group with amyloid. High concentrations of apo A-I in the arterial intima are probably of greater importance to amyloid formation than high plasma levels of the protein. During atherosclerosis, the acute phase reactant serum amyloid A may displace apo A-I from HDL, leading to increased concentration of lipid-free apo A-I in the intima and conformational changes of apo A-I, which make it more fibrillogenic. Some forms of amyloid fibrils have been shown to be cytotoxic. Apo A-I-derived amyloid is possibly a pathogenically important factor in atherosclerosis.

Apolipoprotein A-1-derived amyloid in atherosclerotic plaques of the human aorta

Previous studies have shown that the amyloid localized to the aortic intima may be a biochemical entity different from other forms of localized amyloid. The amyloid fibril protein in one patient studied consisted of an N-terminal fragment of apolipoprotein A-1 (apo A-1). Since this patient was later shown to carry a missense mutation in the apo A-1 gene, leading to a deletion at position 107 of the mature protein, the question remained whether wild-type apo A-1 is amyloidogenic. In autopsy specimens from the thoracic aorta from 69 individuals, intimal atherosclerotic plaque-related amyloid was present in 11 cases (16%) and amyloid outside plaques in 37 cases (54%). The immunoreactivity of amyloid localized to the aortic intima was evaluated with the aid of antisera against N-terminal segments of apo A-1. The amyloid in association with atherosclerotic plaques was positively labelled by immunohistochemistry. The amyloid fibril protein from one patient, previously shown not to carry any mutation in the apo A-1 gene, was purified and shown by amino acid sequence analysis to be of apo A-1 nature. The result shows that wild-type apo A-1 is amyloidogenic and gives rise to a common localized form of amyloid associated with atherosclerosis.

Islet amyloid development in a mouse strain lacking endogenous islet amyloid polypeptide (IAPP) but expressing human IAPP

BACKGROUND

Several mouse strains expressing human islet amyloid polypeptide (IAPP) have been created to study development of islet amyloid and its impact on islet cell function. The tendency to form islet amyloid has varied strongly among these strains by factors that have not been elucidated. Because some beta cell granule components are known to inhibit IAPP fibril formation in vitro, we wanted to determine whether a mouse strain expressing human IAPP but lacking the nonamyloidogenic mouse IAPP is more prone to develop islet amyloidosis.

MATERIALS AND METHODS

Such a strain was created by cross-breeding a transgenic mouse strain and an IAPP null mouse strain.

RESULTS

When fed a fat-enriched diet, male mice expressing only human IAPP developed islet amyloid earlier and to a higher extent than did mice expressing both human and mouse IAPP. Supporting these results, we found that mouse IAPP dose-dependently inhibits formation of fibrils from human IAPP.

CONCLUSIONS

Female mice did not develop amyloid deposits, although small extracellular amorphous IAPP deposits were found in some islets. When cultivated in vitro, amyloid deposits occurred within 10 days in islets from either male or female mice expressing only human IAPP. The study shows that formation of islet amyloid may be dependent on the environment, including the presence or absence of fibril inhibitors or promoters.

Liver transplantation as rescue treatment in a patient with primary AL kappa amyloidosis

Although involvement of the liver is common in systemic amyloidosis, clinical manifestations of hepatic dysfunction and liver biochemical abnormalities are often absent or only mild. Here we report on a patient with primary amyloidosis and rapid development of liver failure, who was successfully treated by liver transplantation. The patient is a 61-year-old Swedish man who was admitted to the local hospital for spontaneous rupture of the spleen. Before admission, he had suffered from diffuse upper abdominal discomfort, diminished appetite, and had lost 15 kg in 6 months. Shortly after splenectomy, he developed cholestatic liver failure with moderate hepatomegaly, jaundice, ascites and hyponatremia. Over a period of 3 weeks his liver failure progressed, renal function deteriorated rapidly, and he developed encephalopathy. Liver transplantation was performed on the 35th day after splenic rupture. Histological examination revealed extensive deposits of amyloid in the spleen and liver. N-terminal amino acid sequence analysis of the amyloid protein, purified from the patient's native liver, revealed an AL protein of kappa I-type origin. The postoperative course was uncomplicated, apart from one episode of sepsis and one course of treatment for acute rejection. He was discharged from hospital with normal liver function and good kidney function. One year after surgery, he was in good condition, with normal liver function. However, a liver biopsy taken at the same time showed de novo amyloid deposits in the grafted liver. We conclude that liver transplantation may be indicated as a life-saving procedure in rapidly progressing hepatic amyloidosis with cholestatic jaundice, although the underlying disease has not changed.

Amyloid in human islets of Langerhans: immunologic evidence that islet amyloid polypeptide is modified in amyloidogenesis

Amyloid derived from the beta-cell product islet amyloid polypeptide (IAPP) has been implicated for a beta-cell lesion in Type II diabetes mellitus. The pathogenesis of islet amyloid is poorly understood, and in addition to an amyloidogenic IAPP molecule and possibly increased concentration of IAPP, other unknown factors seem to be included. It was shown previously that polyclonal rabbit IAPP antisera label beta cells close to amyloid only weakly. Whether this lack of immunoreactivity depends on lack of IAPP or on hidden epitopes is in question. In the present study, we show that the IAPP immunoreactivity of these beta cells is possible to retrieve. On the other hand, the monoclonal IAPP antibody 4A5, which labels IAPP in beta cells, does not label IAPP in its native amyloid form. We show evidence that this lack of immunoreactivity is not dependent on conformational change of the IAPP molecules in the amyloidogenesis but is likely owing to glycation of IAPP in human islet amyloid deposits.

Pro islet amyloid polypeptide (ProIAPP) immunoreactivity in the islets of Langerhans

Islet amyloid is typically found in type 2 diabetes mellitus and is believed to participate in the beta cell deterioration. The islet amyloid fibril consists of the 37-amino-acid islet amyloid polypeptide (IAPP) but its pathogenesis is only partly understood. We developed several different rabbit antisera against the flanking peptides of the IAPP precursor (proIAPP) and the proIAPP processing sites in order to study the possible occurrence of unprocessed proIAPP or parts thereof in islet amyloid. We applied these antisera in an immunohistochemical study on, islet amyloid deposits present in a newly generated mouse strain that over-expresses human IAPP but is devoid of mouse IAPP. Male mice of this strain develop severe islet amyloidosis when given a high fat diet. Generally, the antisera showed no immunoreactivity with the amyloid. However, in scattered single beta cells, where amyloid could be seen intracellularly, immunoreactivity with one or more of the antisera co-localized with the amyloid. Although virtually all amyloid in human islets of Langerhans is found extracellularly, we propose that the initial amyloid formation occurs intracellularly, perhaps by not fully processed or folded (pro)IAPP. This amyloid, which may develop rapidly under certain circumstances, probably leads to cell death. If not degraded these amyloid spots may then act as nidus for further amyloid formation from fully processed IAPP, secreted from surrounding beta cells.

Medin: an integral fragment of aortic smooth muscle cell-produced lactadherin forms the most common human amyloid

Aortic medial amyloid is a form of localized amyloid that occurs in virtually all individuals older than 60 years. The importance and impact of the amyloid deposits are unknown. In this study we have purified a 5.5-kDa aortic medial amyloid component, by size-exclusion chromatography and RP-HPLC, from three individuals, and we have shown by amino acid sequence analysis that the amyloid is derived from an integral proteolytic fragment of lactadherin. Lactadherin is a 364-aa glycoprotein, previously known to be expressed by mammary epithelial cells as a cell surface protein and secreted as part of the milk fat globule membrane. The multidomain protein has a C-terminal domain showing homology to blood coagulation factors V and VIII. We found that the main constituent of aortic medial amyloid is a 50-aa-long peptide, here called medin, that is positioned within the coagulation factor-like domain of lactadherin. Our result is supported by the specific labeling of aortic medial amyloid in light and electron microscopy with two rabbit antisera raised against two synthetic peptides corresponding to different parts of medin. By using in situ hybridization we have shown that lactadherin is expressed by aortic medial smooth muscle cells. Furthermore, one of the synthetic peptides forms amyloid-like fibrils in vitro. Lactadherin was not previously known to be an amyloid precursor protein or to be expressed in aortic tissue. The structure of lactadherin may implicate an important regulatory function in the aorta.

What is the role of giant cells in AL-amyloidosis?

AL-amyloidosis is one of the most common amyloidoses and can be found in a localized and a systemic form. The precursor protein is an immunoglobulin light chain which as AL-protein in both localized and systemic AL-amyloidosis shows the same pattern of fragmentation and changes of primary structure. In this work it is shown that that there is a difference between localized and systemic amyloidosis in respect to accompanying giant cells which constantly are found associated with amyloid deposits in localized AL-amyloidosis. In addition, giant cells were found together with amyloid deposits in lymph nodes of some cases of systemic AL-amyloidosis. Based on these findings and electron microscopic studies, it is discussed whether the giant cells actively participate in amyloid fibril formation by uptake and modification of the precursor protein or the giant cells are part of a foreign body reaction. Included in this work are two new cases of localized lung (lambda I) and ureteric (kappa I) AL-amyloidosis.

Islet amyloid polypeptide and insulin relationship in a longitudinal study of the genetically obese (ob/ob) mouse

Obese mice (Umeå ob/ob) and their lean litter-mates were investigated from 7 to 52 weeks of age with respect to the plasma concentration of islet amyloid polypeptide (IAPP) and insulin. Plasma levels of IAPP were highly elevated in the ob/ob mice and remained unchanged until age 33 weeks, after which a sudden significant increase occurred at age 40 weeks. The plasma concentration of insulin gradually increased from start to end and reached extremely high levels. In the lean mice, there were no age-related differences in plasma levels of IAPP and insulin, being of the same magnitude as in normal NMRI mice. The plasma IAPP/insulin molar ratio was similar in lean and obese mice until age 14 weeks. At 21 weeks, the ratio in the ob/ob mice had decreased dramatically and remained markedly (sixfold) lower than in the lean mice until the end of the study. The IAPP concentration in the pancreata of 21-week-old ob/ob mice was 25-fold higher than that in the lean mice. Immunohistochemically, a majority of the ob/ob mice displayed enlarged and more numerous pancreatic islets, compared with the lean mice, and the IAPP- and insulin-labeling intensity was equal for all animals. At the electron-microscopic level, there was an increase in the number of IAPP- and insulin-immunoreactive gold particles per whole granule area as well as per core granule area. We conclude that the dramatically increased IAPP levels in severely hyperinsulinemic ob/ob mice may be of importance for the development of insulin resistance. Further, the disproportionate secretion of IAPP and insulin in the adult obese mouse might indicate a disturbed negative feedback effect of IAPP on insulin secretory mechanisms, resulting in very high plasma insulin levels.

Differences in amyloid deposition in islets of transgenic mice expressing human islet amyloid polypeptide versus human islets implanted into nude mice

Islet amyloid polypeptide (IAPP)-derived amyloid is frequently deposited in the islets of Langerhans in patients with chronic non-insulin-dependent diabetes mellitus (NIDDM). When human islets were implanted under the renal capsule in nude mice, amyloid occurred in 73% of the grafts within 2 weeks. In this study, we compare the deposition of amyloid in islets from a transgenic mouse strain expressing human IAPP (hIAPP) and in normal human islets after implantation in nude mice. The implantations were performed as follows: (1) nondiabetic recipients were given islets from transgenic mice alone, (2) human islets were implanted in the upper pole of the kidney and islets from transgenic mice were implanted in the lower pole of the kidney, (3) grafts containing a mixture of human and transgenic islets were implanted, and (4) transgenic islets and islets from nontransgenic littermates were implanted in therapeutic numbers into recipients made diabetic by a single injection of alloxan prior to implantation. The implants were removed after various periods from 4 days to 8 weeks. The implants were either fixed in Formalin, stained for amyloid, and viewed in polarized light, or processed for immunoelectron microscopy and studied after immunolabeling with specific antibodies against IAPP. We found that the course of amyloid deposition differed significantly between human islets and hIAPP-expressing mouse islets. In human islets, amyloid was mainly deposited intracellularly and only small amounts of amyloid were found extracellularly. In contrast, in islets from transgenic mice, amyloid was exclusively deposited extracellularly and deposition in this site was preceded by an aggregation of immunoreactive material along the basement membrane. These findings point to separate mechanisms for amyloid formation in these two models.

Cutaneous malignant melanoma in Swedish children and teenagers 1973-1992: a clinico-pathological study of 130 cases

To assess whether there has been a change in histological features and prognostic factors of primary cutaneous malignant melanoma (CMM) in young individuals in Sweden, an unselected, population-based study was undertaken; 177 cases of primary CMM in persons below 20 years of age were reported to the Swedish National Cancer Registry between 1973 and 1992. In 87% of the cases, original tumor tissue was available for histo-pathological review. The original diagnosis was verified in 88% (n = 126) of these cases. All tumors had histological features similar to adult CMM; 17% had an associated precursor lesion. Superficial spreading melanoma (SSM) was the most common sub-type, constituting 20/36 cases in the first decade and 59/90 in the second. Corresponding figures for nodular melanoma (NM) were 11/36 and 23/90. Only 5 melanomas in situ were diagnosed. In girls, the mean thickness of SSM decreased from 1.5 to 0.6 mm (p < 0.001). Overall mortality was 10%, 22% in the group with CMM diagnosed 0-15 years of age and 8% in individuals 15-19 years. Fatal CMM cases diagnosed below 15 years of age (n = 4) were NM > 1.6 mm thick and in subjects 15-19 years (n = 9) 44% of fatal tumors were NM with a mean thickness of 2.2 mm. Breslow index was the single most important prognostic factor. However, when known prognostic factors were adjusted for in a Cox regression analysis, young age remained an independent risk factor, with a relative death rate of 0.21 for individuals aged 15-19 compared with children < 15 years of age.

The use of subcutaneous fat tissue for amyloid typing by enzyme-linked immunosorbent assay

The amyloidoses are biochemically heterogeneous diseases with pathophysiologic deposits of various proteins. The clinical course, prognosis, and therapy are different for each type of amyloidosis and, therefore, a type-specific diagnosis is demanded as early as possible. We describe a method for typing the most common systemic amyloidoses of AL, AA, and transthyretin types by enzyme-linked immunosorbent assay (ELISA), using abdominal wall subcutaneous fat biopsy specimens. The method was tested on 21 abdominal fat biopsy specimens that were sent to the laboratory. Of these, 15 contained amyloid that was successfully characterized in 14 cases. One specimen contained amyloid that did not react with any antisera used. The 6 specimens without amyloid gave no reaction in ELISA. The described ELISA method is reliable and easy to perform, and the tissue sample needed is obtained by minor surgery.

Quantitative immunohistochemical analysis of islet amyloid polypeptide (IAPP) in normal, impaired glucose tolerant, and diabetic cats

Islet amyloid polypeptide (IAPP, "amylin") has been proposed as having important roles in the pathogenesis of type 2 diabetes mellitus via its biological activity and by forming islet amyloid. The domestic cat develops a type of diabetes that closely resembles type 2 diabetes in humans, including the frequent formation of islet amyloid deposits in the impaired glucose tolerant (IGT) and diabetic state. With the aid of computerized image analysis and immunohistochemistry, we examined the IAPP and insulin content in pancreatic islets of normal, IGT and diabetic cats. IAPP immunoreactivity in beta cells from IGT cats was significantly stronger (p < 0.01) as compared with cells from normal cats, while the insulin labelling strength was unchanged. Overtly diabetic cats were usually almost devoid of beta cells. As in humans, cellular IAPP but not IAPP in islet amyloid deposits was labelled by the newly developed monoclonal antibody to IAPP 4A5, thus providing further evidence that IAPP is modified by a yet unknown mechanism during the amyloidogenic process. The study provides evidence that an increased beta cell storage of IAPP independent of insulin may be an important factor in the early phase of the development of islet amyloid in this form of diabetes.

Fragments of the constant region of immunoglobulin light chains are constituents of AL-amyloid proteins

Immunoglobulin light chains are the precursor proteins of AL-amyloidosis. In the fibril formation process properties of the variable part of the immunoglobulin light chains are believed to be of major importance. In this work it is shown that fragments of the constant part of the immunoglobulin light chain are a constituent of the AL-amyloid proteins of kappa type. A specific antiserum has identified these fragments in gel filtration fractions where the absorbance approached the base line after the main retarded peak. The fragments are small and have been overlooked previously in the purification process. The significance of the constant part in AL-proteins is unclear, but adds new aspects to the discussion of pre- or post-fibrillogenic cleavage of the immunoglobulin light chains.

Increased insulin secretion and glucose tolerance in mice lacking islet amyloid polypeptide (amylin)

Islet amyloid polypeptide (IAPP or amylin) is costored and cosecreted with insulin and may regulate insulin secretion and blood glucose handling. However, the role and importance of endogenous IAPP in the regulation of insulin release and glucose homeostasis have been controversial. Here we report on the generation and phenotypic analysis of IAPP-deficient mice. These mice have normal, or near to normal, basal levels of circulating insulin and glucose. However, following glucose administration, IAPP-deficient males presented increased insulin responses paralleled with a more rapid blood glucose elimination compared to wild-type controls. Blood glucose elimination was also found to be enhanced in IAPP-deficient females, but the insulin response in this gender did not differ from controls. In a transgenic rescue experiment, using an insulin-promoter human-IAPP fusion gene, insulin responses and blood glucose elimination were reversed in IAPP-deficient males, whereas the female phenotype appeared unaffected. Our results provide the first firm evidence of a physiological role for endogenous IAPP and indicate that IAPP, apparently in a gender-dependent manner, limits the degree of glucose-induced insulin secretion and the rate of blood glucose elimination.

Increasing incidence of cutaneous malignant melanoma in children and adolescents 12-19 years of age in Sweden 1973-92

One-hundred-and-seventy-seven cases of cutaneous malignant melanoma were reported to the Swedish National Cancer Registry in subjects below the age of 20 during the period 1973-92. One-hundred-and-fifty-four (87%) were re-examined histologically, and the original diagnosis of primary cutaneous malignant melanoma was verified in 88%. The age-specific mean annual incidence rate increased to 0.5/100,000 in 1983-92 from 0.2/100,000 in 1973-82. Cutaneous malignant melanoma remained extremely rare in children below the age of 12, where only two cases were found. In subjects aged 12-19, the incidence doubled to 93 cases in the second 10-year period compared to 41 in the first. In boys, most of the melanomas occurred on the trunk, and, in girls, on the legs. Sixty-three percent of the melanomas were of the superficial spreading type, which also was the most rapidly increasing type of melanoma. These results emphasize the importance of surveillance and intensified preventive measures in protecting children and adolescents from the harmful effects of excessive exposure to the sun.

Constant region of a kappa III immunoglobulin light chain as a major AL-amyloid protein

AL-amyloidoses are generally described as a group of disorders in which N-terminal fragments of monoclonal immunoglobulin light chains are transferred into amyloid fibrils. We have, by amino acid sequence analyses and immunological methods, characterized the Bence-Jones protein and the corresponding AL protein as a kappa III immunoglobulin light chain from material of a patient with systemic AL-amyloidosis presenting as a local inguinal tumour. The two proteins showed some unique features. The major part of the AL amyloid fibril protein consisted of C-terminal fragments of the Bence-Jones protein. Furthermore, both the Bence-Jones protein and the AL protein were glycosylated, with possibly a glycosylation in the constant part of the light chain.

Increased release of IAPP in response to long-term high fat intake in mice

In the present study, mice were fed high-fat diet or standard animal chow during 6 months. Animals fed high-fat diet showed a 4.5-fold increase in the fasting plasma IAPP levels compared to animals fed standard chow. No significant change in plasma insulin levels occurred between the groups. These differences in hormone response result in a change of the molar ratio between IAPP and insulin in the group fed high-fat diet. An increased IAPP to insulin molar ratio might be important in the pathogenesis of islet amyloid in man.

Extended analysis of AL-amyloid protein from abdominal wall subcutaneous fat biopsy: kappa IV immunoglobulin light chain

In AL-amyloidosis the cause of amyloid fibril formation in beta-pleated sheets from the precursor protein immunoglobulin light chain is not established, but studies of AL-proteins indicate that amino acid substitutions are important in the pathogenesis. Amyloid material was extracted from a subcutaneous fat tissue biopsy and submitted to extended protein separation, typing and amino acid sequence analyses. The AL-protein belonged to the rare immunoglobulin light chain kappa, subtype kappa IV and contained unique amino acid substitutions, mostly in the highly preserved framework regions. The study shows that subcutaneous fat biopsies are useful sources of amyloid material for biochemical studies.

Acceleration of amyloid protein A amyloidosis by amyloid-like synthetic fibrils

Amyloid protein A (AA) amyloidosis is a consequence of some long-standing inflammatory conditions, and subsequently, an N-terminal fragment of the acute phase protein serum AA forms beta-sheet fibrils that are deposited in different tissues. It is unknown why only some individuals develop AA amyloidosis. In the mouse model, AA amyloidosis develops after approximately 25 days of inflammatory challenge. This lag phase can be shortened dramatically by administration of a small amount of amyloid extract containing an as yet undefined amyloid-enhancing factor. In the present study, we show that preformed amyloid-like fibrils made from short synthetic peptides corresponding to parts of several different amyloid fibril proteins exert amyloidogenic enhancing activity when given i.v. to mice at the induction of inflammation. We followed i.v. administered, radiolabeled, heterologous, synthetic fibrils to the lung and to the perifollicular area in the spleen and found that new AA-amyloid fibrils developed on these preformed fibrils. Our findings thus show that preformed, synthetic, amyloid-like fibrils have an in vivo nidus activity and that amyloid-enhancing activity may occur, at least in part, through this mechanism. Our findings also show that fibrils of a heterologous chemical nature exert amyloid-enhancing activity.