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P Westermark

Publications and source records attributed to P Westermark.

At least 127 records · Page 7Linked to original sources
PubMed1989

Islet amyloid polypeptide (IAPP) and pro-IAPP immunoreactivity in human islets of Langerhans.

Islet amyloid polypeptide (IAPP) is a 37-amino-acid putative hormone which is expressed by islet B-cells and most probably is co-released with insulin. IAPP is synthesized as an 89-amino-acid prepropeptide in which IAPP is flanked by two short peptides. The two short peptides are ultimately cleaved off at basic residues. In the present study, we used antisera to three different synthetic peptides corresponding to positions 18-30, 40-50 and 53-62 of prepro-IAPP. The two latter peptides fall within the mature IAPP molecule while the first peptide corresponds to the N-terminal flanking peptide. We demonstrate that normal B-cells and islet amyloid both react immunohistochemically with all of these antisera. Using the immunogold labelling technique, we also demonstrate electron microscopically that both the IAPP immunoreactivity and the pro1-IAPP immunoreactivity in amyloid deposits are confined to the amyloid fibrils per se. These data indicate that not only mature IAPP but also the N-terminal flanking peptide is present in islet amyloid deposits. It remains to be shown if the propeptide segments are involved in the pathogenesis of these amyloid depositions.

Aged↗
PubMed1989

Islet amyloid, islet-amyloid polypeptide, and diabetes mellitus.

Islet-amyloid deposits, which are a common feature of Type II diabetes mellitus, are derived from the polymerization of a putative hormone identified as IAPP. IAPP is synthesized by normal islet beta cells and probably is cosecreted with insulin. Although the physiologic function of IAPP and its role in the pathogenesis of Type II diabetes mellitus are just beginning to be unraveled, IAPP may play an important part in the development of this most common form of diabetes mellitus by opposing the action of insulin in peripheral tissues. The polymerization of IAPP to form extracellular islet-amyloid deposits may further contribute to the development of Type II diabetes mellitus by destroying islet cells and by disrupting the passage of glucose and hormones to and from them. Substantial evidence indicates that the propensity of IAPP to polymerize and form extracellular amyloid deposits in only certain species (e.g., humans, cats, and raccoons) is directly associated with an intrinsically amyloidogenic part of the molecule--i.e., positions 20 through 29 of IAPP. The inherent amyloidogenicity of IAPP in these species may be further facilitated by increased beta-cell production of IAPP, leading to a high local concentration that predisposes to polymerization. The latter possibility is supported by studies demonstrating that IAPP production by islet beta cells is increased in normoglycemic cats with impaired glucose tolerance. Although increased production of IAPP may initially cause insulin resistance, prolonged overproduction of IAPP may ultimately impair insulin secretion by leading to the progressive deposition of insoluble islet amyloid, a finding apparent in most subjects with overt diabetes. If, as these studies suggest, increased IAPP production is linked to the development of Type II diabetes mellitus, further studies must address the genetic and nongenetic factors that influence this important biologic change in humans and some animal species.

Amino Acid Sequence↗
PubMed1989

Sequence divergence in a specific region of islet amyloid polypeptide (IAPP) explains differences in islet amyloid formation between species.

Amyloid deposits in the islets of Langerhans occur in association with type 2 diabetes mellitus (DM) in humans and cats and consist of a 37-amino-acid polypeptide known as islet amyloid polypeptide (IAPP). In order to find an explanation for the situation that islet amyloid (IA) does not develop in common rodent species, we have deduced the amino acid sequence of the IAPP molecule in mouse, rat and hamster. We find that a specific region of the molecule diverges to a high degree. Synthetic peptides corresponding to this region of human and hamster IAPP were compared for their ability to form amyloid fibrils in vitro. Whereas the human peptide readily formed fibrils with amyloid character, the hamster peptide completely lacked this property. We suggest this to be a likely explanation for the differences in IA formation between humans and rodents and discuss our findings in relation to the type 2 DM syndrome.

Amino Acid Sequence↗
PubMed1989

Co-localization of islet amyloid polypeptide and insulin in the B cell secretory granules of the human pancreatic islets.

Islet amyloid polypeptide is a novel 37 amino-acid-residues polypeptide which has been isolated from amyloid deposits in an insulinoma, and in human and cat islets of Langerhans. The molecule has 46% homology with the calcitonin gene-related peptide. Light microscopy examination of the pancreas shows that islet amyloid polypeptide immunoreactivity is restricted to the islet B cells. The present study utilized a rabbit antiserum against a synthetic peptide corresponding to positions 20-29 of islet amyloid polypeptide, a sequence without any amino-acid identity with calcitonin gene-related peptide. By applying the immunogold technique at the ultrastructural level, it was shown that both insulin and islet amyloid polypeptide immunoreactivity occurs in the central granular core of the human B cell secretory granules, while the A cells remain unlabelled. The demonstration that islet amyloid polypeptide is a granular protein of the B cells may indicate that it is released together with insulin. Further studies are necessary to evaluate the functional role of islet amyloid polypeptide.

Aged↗
PubMed1989

Islet amyloid polypeptide (IAPP):cDNA cloning and identification of an amyloidogenic region associated with the species-specific occurrence of age-related diabetes mellitus.

We have cloned and sequenced a human islet amyloid polypeptide (IAPP) cDNA. A secretory 89 amino acid IAPP protein precursor is predicted from which the 37 amino acid IAPP molecule is formed by amino- and carboxyterminal proteolytic processing. The IAPP peptide is 43-46% identical in amino acid sequence to the two members of the calcitonin gene-related peptide (CGRP) family. Evolutionary conserved proteolytic processing sites indicate that similar proteases are involved in the maturation of IAPP and CGRP and that the IAPP amyloid polypeptide is identical to the normal proteolytic product of the IAPP precursor. A synthetic peptide corresponding to a carboxyteminal fragment of human IAPP is shown to spontaneously form amyloid-like fibrils in vitro. Antibodies against this peptide cross-react with IAPP from species that develop amyloid in pancreatic islets in conjunction with age-related diabetes mellitus (human, cat, racoon), but do not cross-react with IAPP from other tested species (mouse, rat, guinea pig, dog). Thus, a species-specific structural motif in the putative amyloidogenic region of IAPP is associated with both amyloid formation and the development of age-related diabetes mellitus. This provides a new molecular clue to the pathogenesis of this disease.

Amino Acid Sequence↗
PubMed1989

Amino acid sequence variations in protein AA of cats with high and low incidences of AA amyloidosis.

1. Amyloid isolated from the liver of a domestic short-haired (DSH) cat was dissolved and purified by gel filtration for amino acid sequence analysis. 2. Sequences of two major peptides corresponding to positions 18-23 and 25-75 of human amyloid protein AA were obtained when cyanogen bromide-cleaved protein was applied to an amino acid sequenator. 3. Comparison of these regions of amyloid protein from the Abyssinian cat (high incidence of AA amyloidosis) and DSH cat (low incidence of AA amyloidosis) revealed three amino acid differences, two of which occurred within regions that are completely conserved in the Abyssinian cat and all other species. 4. Secondary prediction plots showed less potential for amyloidogenicity (i.e., less beta-sheet conformation) in protein AA of the DSH cat as compared to the Abyssinian cat and other animal species. 5. These differences in protein AA of the DSH cat may, therefore, be linked to the comparatively uncommon occurrence of AA amyloidosis in the DSH cat as compared to the Abyssinian cat and other animals species.

Amino Acid Sequence↗
PubMed1989

Massive vascular AA-amyloidosis: a histologically and biochemically distinctive subtype of reactive systemic amyloidosis.

Amyloid protein AA consists of several subspecies which mainly arise through proteolytic cleavage at various sites of the precursor, serum protein AA. The most common protein AA subspecies (the protein AA prototype) contains 76 amino-acid residues. In previous studies we have shown that distinctive patterns of amyloid infiltration occur in AA-amyloidosis. The amyloid in different patterns of infiltration seems to consist of distinctive protein AA subspecies. In the present study we have analysed protein AA in three patients with a form of AA-amyloidosis with heavy vascular infiltration and show that the amyloid fibrils contain two groups of protein AA subspecies. One, quantitatively predominating, group contains large subspecies of up to 94 amino-acid residues and a second group of protein AA-molecules contains around 50 amino-acid residues. The AA molecules lack the N-terminal arginine residue. It is concluded that AA-amyloidosis with massive vascular infiltration is a distinctive subform with typical clinical and histological appearance and with fibrils containing characteristic protein AA subspecies.

Amino Acid Sequence↗
PubMed1989

Use of subcutaneous abdominal fat biopsy specimen for detailed typing of amyloid fibril protein-AL by amino acid sequence analysis.

A simple technique for the purification of amyloid fibril proteins from patients with systemic amyloidosis was used on a 45 year old woman. The method is based on the use of a surgical subcutaneous fat tissue biopsy specimen which was used for the characterisation of the amyloid as a kappa I AL-protein by amino acid sequence analysis. The method permits the exact typing of amyloid in many patients with systemic amyloidosis, which, until now has been almost exclusively confined to necropsy tissue.

Abdomen↗
PubMed1989

Impaired glucose tolerance is associated with increased islet amyloid polypeptide (IAPP) immunoreactivity in pancreatic beta cells.

Adult cats determined by clinical laboratory evaluations to be normal, impaired glucose tolerant, or overtly diabetic were used to explore prospectively the relationships among pancreatic beta cell islet amyloid polypeptide (IAPP) immunoreactivity, islet amyloid (IA) deposition, and diabetogenesis. IAPP-derived IA was found in 11 of 14 (79%) diabetic cats, in four of nine (44%) impaired glucose tolerant cats, and in two of eight (25%) normal adult cats. The presence of IA even in very small amounts, therefore, predicts a very high probability (88%) that an animal has either impaired glucose tolerance or overt DM. Although all overtly diabetic cats had a marked decrease or absence of beta cell IAPP immunoreactivity, six of six cats with impaired glucose tolerance retained IAPP immunoreactivity with 1:15,000 dilutions of antisynthetic IAPP 7-17, whereas only one of seven normal cats had IAPP immunoreactivity beyond 1:10,000 dilutions. These findings suggest that increased IAPP production preceding the development of overt DM is linked to the progressive formation of insoluble IA deposits that are apparent in most overtly diabetic individuals. Of most importance, in that IAPP has been reported to inhibit both basal and insulin-stimulated rates of glycogen synthesis, is the possibility that increased production and release of IAPP by pancreatic beta cells plays a key role in the development of the insulin resistance and impaired glucose tolerance, both of which occur in Type 2 DM.

Amyloid↗
PubMed1988

Evidence that the amyloid fibril protein in senile systemic amyloidosis is derived from normal prealbumin.

Familial amyloidosis in different kindreds is associated with a variety of point mutations in the prealbumin gene, resulting in prealbumin variants which are believed to be amyloidogenic, i.e. prone to form amyloid fibrils. In the most common amyloid-associated variant, there is a methionine for valine substitution in position 30. We have studied the prealbumin-derived amyloid protein ASc1 in the common age-related senile systemic amyloidosis. Evidence is presented that there is no abnormality in the primary structure of prealbumin in this disease and that, in addition to complete prealbumin, fibrils contain prealbumin fragments lacking a significant part of the N-terminus.

Aged↗
PubMed1988

Insulin as an amyloid-fibril protein at sites of repeated insulin injections in a diabetic patient.

A patient with Type 1 (insulin-dependent) diabetes mellitus developed localised amyloidosis at the sites of his injections of porcine insulin. A major amyloid fibril protein was extracted and, by means of its amino acid composition and amino acid sequence, it was shown to contain intact insulin molecules. Porcine insulin is the tenth protein and the first foreign protein to be chemically identified in human amyloid fibrils.

Adult↗
PubMed1988

AA amyloid-associated gastroenteropathy in a horse.

Systemic amyloidosis involving the digestive tract is described in an 11-year-old Morgan stallion. The disease was characterized clinically by weight loss, ptyalism, anaemia, persistent mature neutrophilia, hypoalbuminaemia and hypergammaglobulinaemia. The D-xylose absorption test indicated malabsorption. Necropsy revealed oral, oesophageal and gastric ulcers and reddened segments of small bowel mucosa with scant haemorrhages. Microscopically, amyloid deposits were found throughout all tissue layers of the digestive tract, except the serosa. Deposits of amyloid were most apparent in the small bowel mucosa and submucosal arteries. Amyloid was also present in the spleen and lymph nodes and to a lesser extent in the liver, kidneys, lungs, pancreas and bone marrow. All amyloid deposits gave the typical histochemical reaction for AA amyloid with the KMnO4-Congo red stain procedure and immunohistochemical cross-reactivity was demonstrated with antisera to both canine and bovine protein AA by the peroxidase-antiperoxidase technique. The cause of the amyloidosis was not identified, although the haematological and serological data were compatible with an underlying chronic inflammatory process.

Amyloidosis↗
PubMed1988

Immunologic studies in identical twins concordant for juvenile rheumatoid arthritis but discordant for monoclonal gammopathy and amyloidosis.

Identical twins concordant for juvenile rheumatoid arthritis but discordant for monoclonal gammopathy and amyloidosis were the subjects of a study done with mixed leukocyte culture, anti-idiotypic antisera against serum and urinary M component from the amyloid-affected twin, and in vitro estimations of M-component idiotype synthesis by peripheral blood mononuclear cells. Immunohistochemical analysis of renal amyloid deposits in the affected twin showed AL amyloid of the lambda-II variable region subgroup. M-component idiotypes were confined only to the twin with serum and urine M components.

Adult↗
PubMed1988

Immunohistochemical identification of heparan sulphate proteoglycan in secondary systemic amyloidosis.

The distribution of proteoglycans in kidneys from patients with secondary (AA) systemic amyloidosis was investigated. Antisera reacting with the protein cores of chondroitin sulphate proteoglycan (CSPG), dermatan sulphate proteoglycan (DSPG) and heparan sulphate proteoglycan (HSPG) were used in conjunction with the peroxidase-antiperoxidase (PAP) method. HSPG was the only proteoglycan found to be specifically localized to the amyloid deposits. The staining was most intense on the endothelial side of the deposits in both the glomeruli and in the vessel walls. No staining was observed after absorption of the HSPG antiserum with a fraction of the amyloid preparations, corresponding in size to that reported for glomerular HSPG. The possible role of HSPG and endothelial cells in the pathogenesis of the amyloid deposits is discussed.

Amyloidosis↗
PubMed1988

Immunolocalization of islet amyloid polypeptide (IAPP) in pancreatic beta cells by means of peroxidase-antiperoxidase (PAP) and protein A-gold techniques.

A novel putative polypeptide hormone identified as islet amyloid polypeptide (IAPP) was recently purified from islet amyloid (IA) of diabetic humans and cats, and also from amyloid of a human insulinoma. Although the function of IAPP is yet unknown, its occurrence in pancreatic endocrine tissue and its partial amino acid sequence identity with calcitonin gene-related peptide (CGRP) suggests an endocrine regulatory effect. In the present investigation, the authors utilized antisera to insulin, glucagon, somatostatin, pancreatic polypeptide, synthetic human CGRP, and a synthetic human IAPP (7-17) undecapeptide to immunohistochemically (PAP technique) document the presence of IAPP immunoreactive cells in the islets of the cat, dog, mouse, and rat, but not in the islets of the horse or calf. In serial sections of islets from these species it was shown that IAPP immunoreactivity occurred in insulin-reactive beta cells. This observation was confirmed immunocytochemically in cat islets by means of protein A-gold probes. With protein A-gold labeling techniques, IAPP immunoreactivity was localized to the outer lucent compartment of the beta cell secretory granule, whereas insulin immunoreactivity was associated with the electron-dense core. These findings provide strong evidence that IAPP or an IAPP precursor is synthesized by beta cells and is stored in beta cell granules for subsequent co-secretion with insulin. The conservation of IAPP in humans and multiple animal species and the localization of IAPP to pancreatic beta cells provide further evidence that IAPP has an important endocrine regulatory function. The propensity of IAPP to polymerize and form IA fibrils in diabetes associated with aging may indicate that IAPP is in some way also linked to the development of Type 2 diabetes.

Amyloid↗