Localized insulin-derived amyloidosis in patients with diabetes mellitus: a case report

Mechanistic Insights Behind the Self-Assembly of Human Insulin under the Influence of Surface-Engineered Gold Nanoparticles

Elucidating the underlying principles of amyloid protein self-assembly at nanobio interfaces is extremely challenging due to the diversity in physicochemical properties of nanomaterials and their physical interactions with biological systems. It is, therefore, important to develop nanoscale materials with dynamic features and heterogeneities. In this work, through engineering of hierarchical polyethylene glycol (PEG) structures on gold nanoparticle (GNP) surfaces, tailored nanomaterials with different surface properties and conformations (GNPs-PEG) are created for modulating the self-assembly of a widely studied protein, insulin, under amyloidogenic conditions. Important biophysical studies including thioflavin T (ThT) binding, circular dichroism (CD), surface plasmon resonance (SPR), and atomic force microscopy (AFM) showed that higher-molecular weight GNPs-PEG triggered the formation of amyloid fibrils by promoting adsorption of proteins at nanoparticle surfaces and favoring primary nucleation rate. Moreover, the modulation of fibrillation kinetics reduces the overall toxicity of insulin oligomers and fibrils. In addition, the interaction between the PEG polymer and amyloidogenic insulin examined using MD simulations revealed major changes in the secondary structural elements of the B chain of insulin. The experimental findings provide molecular-level descriptions of how the PEGylated nanoparticle surface modulates protein adsorption and drives the self-assembly of insulin. This facile approach provides a new avenue for systematically altering the binding affinities on nanoscale surfaces by tailoring their topologies for examining adsorption-induced fibrillogenesis phenomena of amyloid proteins. Together, this study suggests the role of nanobio interfaces during surface-induced heterogeneous nucleation as a primary target for designing therapeutic interventions for amyloid-related neurodegenerative disorders.

Amyloidoma: A Case Report of Remote Insulin-Derived Amyloidosis in the Setting of Insulin-Dependent Diabetes

The incidence of insulin-induced amyloidosis distant from an injection site is unknown. Due to its rare nature, only a few case reports have been reported, with even fewer describing amyloidoma as distant from the insulin injection site. We present a case of a 52-year-old male with a left arm mass that was determined to be cutaneous amyloidosis and successfully treated with total excision of the mass. Histopathological examination with Congo red stain demonstrated classic characteristics of amyloidosis. We present this case report to increase awareness of this relatively rare occurrence.

Differences in clinicopathological characteristics between lipohypertrophy and localized insulin-derived amyloidosis: A scoping review

Insulin is used as a therapeutic agent in patients with diabetes, and cutaneous lipohypertrophy (LH) and localized insulin-derived amyloidosis (LIDA) are well-known adverse effects associated with insulin injections. The clinical implications, management, assessment methods, and pathological differentiation of LH and LIDA have been recently updated. This review was to update our knowledge of the pathological differentiation, effects of insulin absorption, hypoglycemic events, and recent assessment methods for LH and LIDA. A scoping review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta Analyses extension for Scoping Reviews guidelines. Original studies and case reports in English were also included. PubMed and Scopus databases were searched for keywords to identify papers published up to January 2022. A total of 113 studies were identified through a database search, and 31 were eligible for inclusion in this scoping review. In the 31 studies included in this review, patients with type 2 diabetes had high frequencies of LH and LIDA. LH outcome parameters were assessed using pathological findings and imaging. LIDA is mainly determined by pathological methods, such as hematoxylin and eosin and Congo red staining. Several in vitro and in vivo LIDA models of LIDA have been developed. These results suggest that pathological analysis is required to identify LH and LIDA. It is important to consider LIDA, as it likely influences insulin adsorption and glycemic control. Although several studies have evaluated the LIDA process, little is known about the mechanisms underlying the development of adverse effects associated with insulin injections.

Amyloid Fibrils of Pisum sativum L. Vicilin Inhibit Pathological Aggregation of Mammalian Proteins

Although incurable pathologies associated with the formation of highly ordered fibrillar protein aggregates called amyloids have been known for about two centuries, functional roles of amyloids have been studied for only two decades. Recently, we identified functional amyloids in plants. These amyloids formed using garden pea Pisum sativum L. storage globulin and vicilin, accumulated during the seed maturation and resisted treatment with gastric enzymes and canning. Thus, vicilin amyloids ingested with food could interact with mammalian proteins. In this work, we analyzed the effects of vicilin amyloids on the fibril formation of proteins that form pathological amyloids. We found that vicilin amyloids inhibit the fibrillogenesis of these proteins. In particular, vicilin amyloids decrease the number and length of lysozyme amyloid fibrils; the length and width of β-2-microglobulin fibrils; the number, length and the degree of clustering of β-amyloid fibrils; and, finally, they change the structure and decrease the length of insulin fibrils. Such drastic influences of vicilin amyloids on the pathological amyloids' formation cause the alteration of their toxicity for mammalian cells, which decreases for all tested amyloids with the exception of insulin. Taken together, our study, for the first time, demonstrates the anti-amyloid effect of vicilin fibrils and suggests the mechanisms underlying this phenomenon.

Localized Insulin-Derived Amyloidosis in Diabetes Mellitus Type 1 Patient: A Case Report

Localized insulin-derived amyloidosis (LIDA) is a rare local complication of subcutaneous insulin application occurring in patients with diabetes type 1 and 2. A 45-year-old woman with an 11-year history of insulin-dependent diabetes mellitus type 1 underwent a mini-abdominoplasty and excision of a long-standing palpable mass in left hypogastric subcutaneous tissue in the area of long-term insulin application. Histopathological examination revealed insulin amyloidosis as a substrate of the mass lesion. Several months after surgery, there was a transient improvement in previously poor diabetes compensation. In addition to local allergic reactions, abscess formation, scarring, lipoatrophy/dystrophy, and lipohypertrophy, LIDA broadens the differential diagnostic spectrum of local insulin injection complications. LIDA has been described as a cause of poor glycemia compensation, probably due to the conversion of soluble insulin into insoluble amyloid fibrils, which prevents insulin from circulating in the blood and regulating glucose blood concentration. Improvement in diabetes compensation has been described in several reports, including our case. LIDA is a rare local complication of subcutaneous insulin application; accurate diagnosis and treatment have clinical consequences. Immunohistochemical or immunofluorescence distinction from other amyloid types is highly recommended.

Surface-modified cerium dioxide nanoparticles with improved anti-amyloid and preserved nanozymatic activity

Cerium dioxide nanoparticles (CeO₂ NPs) are used increasingly in nanotechnology and particularly in biotechnology and bioresearch. Thus, CeO₂ NPs have been successfully tested in vitro as a potential therapeutic agent for various pathologies associated with oxidative stress, including the formation of protein amyloid aggregates. In this study, to increase the anti-amyloidogenic efficiency and preserve the antioxidant potential, the surface of the synthesized CeO₂ NPs is modified with a nonionic, sugar-based surfactant, dodecyl maltoside (DDM), which is known for its high anti-amyloidogenic activity and biocompatibility. Dynamic light scattering and Fourier transform infrared spectroscopy demonstrated successful modification by DDM. The apparent hydrodynamic diameters of CeO₂ NPs and DDM-modified NPs (CeO₂@DDM NPs) are found to be ⁓180 nm and ⁓260 nm, respectively. A positive zeta potential value of + 30.5 mV for CeO₂ NPs and + 22.5 mV for CeO₂ @DDM NPs suggest sufficient stability and good dispersion of NPs in an aqueous solution. A combination of Thioflavin T fluorescence analysis and atomic force microscopy is used to assess the effect of nanoparticles on the formation of insulin amyloid fibrils. Results show that the fibrillization of insulin is inhibited by both, naked and modified NPs in a dose-dependent manner. However, while the IC₅₀ of naked NPs is found to be ∼270 ± 13 µg/mL, the surface-modified NPs are 50% more efficient with IC₅₀ equaled to 135 ± 7 µg/mL. In addition, both, the naked CeO₂ NPs and DDM-modified NPs displayed an antioxidant activity expressed as oxidase-, catalase- and SOD-like activity. Therefore, the resulting nanosized material is very well suited to prove or disprove the hypothesis that oxidative stress plays a role in the formation of amyloid fibrils.

Insulin-Derived Cutaneous Amyloidosis: A Possible Complication of Repeated Insulin Injections

Primary localized cutaneous amyloidosis (PLCA) is characterized by extracellular deposition of pathological fibril aggregation of proteins in the skin without systemic involvement. Macular amyloidosis, lichen (papular) amyloidosis, and nodular amyloidosis are three different subtypes of PLCA. Although the pathological mechanism of PLCA has not yet been clarified, it is assumed that a nucleus formation of amyloid fibril is formed due to repeated external stimulation, such as subcutaneous injection, which often poses diagnostic challenges. Herein, we present a 54-year-old Korean male patient with cutaneous localized amyloidosis which occurred after repeated local insulin injections, and discuss the relationship between insulin therapy in patients with diabetes mellitus and dermal amyloid deposition.

Enhanced hexamerization of insulin via assembly pathway rerouting revealed by single particle studies

Insulin formulations with diverse oligomerization states are the hallmark of interventions for the treatment of diabetes. Here using single-molecule recordings we firstly reveal that insulin oligomerization can operate via monomeric additions and secondly quantify the existence, abundance and kinetic characterization of diverse insulin assembly and disassembly pathways involving addition of monomeric, dimeric or tetrameric insulin species. We propose and experimentally validate a model where the insulin self-assembly pathway is rerouted, favoring monomeric or oligomeric assembly, by solution concentration, additives and formulations. Combining our practically complete kinetic characterization with rate simulations, we calculate the abundance of each oligomeric species from nM to mM offering mechanistic insights and the relative abundance of all oligomeric forms at concentrations relevant both for secreted and administrated insulin. These reveal a high abundance of all oligomers and a significant fraction of hexamer resulting in practically halved bioavailable monomer concentration. In addition to providing fundamental new insights, the results and toolbox presented here can be universally applied, contributing to the development of optimal insulin formulations and the deciphering of oligomerization mechanisms for additional proteins.

Direct observation of heterogeneous formation of amyloid spherulites in real-time by super-resolution microscopy

Protein misfolding in the form of fibrils or spherulites is involved in a spectrum of pathological abnormalities. Our current understanding of protein aggregation mechanisms has primarily relied on the use of spectrometric methods to determine the average growth rates and diffraction-limited microscopes with low temporal resolution to observe the large-scale morphologies of intermediates. We developed a REal-time kinetics via binding and Photobleaching LOcalization Microscopy (REPLOM) super-resolution method to directly observe and quantify the existence and abundance of diverse aggregate morphologies of human insulin, below the diffraction limit and extract their heterogeneous growth kinetics. Our results revealed that even the growth of microscopically identical aggregates, e.g., amyloid spherulites, may follow distinct pathways. Specifically, spherulites do not exclusively grow isotropically but, surprisingly, may also grow anisotropically, following similar pathways as reported for minerals and polymers. Combining our technique with machine learning approaches, we associated growth rates to specific morphological transitions and provided energy barriers and the energy landscape at the level of single aggregate morphology. Our unifying framework for the detection and analysis of spherulite growth can be extended to other self-assembled systems characterized by a high degree of heterogeneity, disentangling the broad spectrum of diverse morphologies at the single-molecule level.

Real-time super-resolution microscopy analysis reveals the growth kinetics, morphology, and abundance of human insulin amyloid spherulites with different growth pathways.

Dual-Functional Antioxidant and Antiamyloid Cerium Oxide Nanoparticles Fabricated by Controlled Synthesis in Water-Alcohol Solutions

Oxidative stress is known to be associated with a number of degenerative diseases. A better knowledge of the interplay between oxidative stress and amyloidogenesis is crucial for the understanding of both, aging and age-related neurodegenerative diseases. Cerium dioxide nanoparticles (CeO₂ NPs, nanoceria) due to their remarkable properties are perspective nanomaterials in the study of the processes accompanying oxidative-stress-related diseases, including amyloid-related pathologies. In the present work, we analyze the effects of CeO₂ NPs of different sizes and Ce⁴⁺/Ce³⁺ ratios on the fibrillogenesis of insulin, SOD-like enzymatic activity, oxidative stress, biocompatibility, and cell metabolic activity. CeO₂ NPs (marked as Ce1–Ce5) with controlled physical–chemical parameters, such as different sizes and various Ce⁴⁺/Ce³⁺ ratios, are synthesized by precipitation in water–alcohol solutions. All synthesized NPs are monodispersed and exhibit good stability in aqueous suspensions. ThT and ANS fluorescence assays and AFM are applied to monitor the insulin amyloid aggregation and antiamyloid aggregation activity of CeO₂ NPs. The analyzed Ce1–Ce5 nanoparticles strongly inhibit the formation of insulin amyloid aggregates in vitro. The bioactivity is analyzed using SOD and MTT assays, Western blot, fluorescence microscopy, and flow cytometry. The antioxidative effects and bioactivity of nanoparticles are size- or valence-dependent. CeO₂ NPs show great potential benefits for studying the interplay between oxidative stress and amyloid-related diseases, and can be used for verification of the role of oxidative stress in amyloid-related diseases.

Structural changes in selected human proteins induced by exposure to quantum dots, their biological relevance and possible biomedical applications

Quantum dots (QDs) are semi-conductor luminescent nanocrystals usually of 2-10 nm diameter, attracting the significant attention in biomedical studies since emerged. Due to their unique optical and electronic properties, i.e. wide absorption spectra, narrow tunable emission bands or stable, bright photoluminescence, QDs seem to be ideally suited for multi-colour, simultaneous bioimaging and cellular labeling at the molecular level as new-generation probes. A highly reactive surface of QDs allows for conjugating them to biomolecules, what enables their direct binding to areas of interest inside or outside the cell for biosensing or targeted delivery. Particularly protein-QDs conjugates are current subjects of research, as features of QDs can be combined with protein specific functionalities and therefore used as a complex in variety of biomedical applications. It is known that QDs are able to interact with cells, organelles and macromolecules of the human body after administration. QDs are reported to cause changes at proteins level, including unfolding and three-dimensional structure alterations which might hamper proteins from performing their physiological functions and thereby limit the use of QD-protein conjugates in vivo. Moreover, these changes may trigger unwanted cellular outcomes as the effect of different signaling pathways activation. In this review, characteristics of QDs interactions with certain human proteins are presented and discussed. Besides that, the following manuscript provides an overview on structural changes of specific proteins exposed to QDs and their biological and biomedical relevance.

Quantitative evaluation of insulin-induced abdominal subcutaneous dystrophic tissue using shear wave elastography

Aims/Introduction

Subcutaneous dystrophic tissue (DT) produced by insulin injection causes dysglycemia owing to inadequate absorption of insulin. However, precise techniques for measuring DT have not been established. Shear wave elastography (SWE) is an imaging technology that can quantify tissue stiffness. In this study, insulin injection‐induced DT was quantified using SWE to generate whole‐abdominal wall subcutaneous tissue by three‐dimensional (3D) imaging in patients with type 2 diabetes who were treated with multiple insulin injections.

Materials and Methods

Seven patients with type 2 diabetes were recruited who received long‐standing multiple insulin injections. Using SWE, the shear wave velocity (SWV) of DT and control (normal subcutaneous tissue) was measured. Furthermore, two of seven patients underwent whole‐abdominal SWE examination to calculate the proportion of DT. A subcutaneous insulin tolerance test was also performed in both the DT and control tissues.

Results

The SWV in DT was significantly higher than that in the control tissue (2.87 [2.66–2.98] vs 1.29 [1.23–1.44] m/s, P < 0.01). The proportion of the DT volume was 0.67% and 5.21% for two individuals from the entire abdominal subcutaneous tissue volume. The area under the curve for the subcutaneously injected insulin aspart concentration at the DT sites was lower than that of the control tissue (75.0 [52.1–111] vs 116 [86.9–152.5] h*mU/L, P = 0.1).

Conclusions

SWE can be useful in quantifying abdominal subcutaneous insulin‐induced DT, especially the 3D volume of insulin injection‐induced DT from the entire abdominal subcutaneous tissue. This study is the first to examine the volume and distribution of abdominal subcutaneous DT using SWE.

Modulating Insulin Aggregation with Charge Variable Cholic Acid-Derived Polymers

To understand the effect of cholic acid (CA)-based charge variable polymeric architectures on modulating the insulin aggregation process, herein, we have designed side-chain cholate-containing charge variable polymers. Three different types of copolymers from 2-(methacryloyloxy)ethyl cholate with anionic or cationic or neutral units have been synthesized by reversible addition-fragmentation chain transfer polymerization. The effects of these copolymers on the insulin fibrillation process was studied by multiple biophysical approaches including different types of spectroscopic and microscopic analyses. Interestingly, the CA-based cationic polymer (CP-10) was observed to inhibit the insulin fibrillation process in a dose-dependent manner and to act as an effective anti-amyloidogenic agent. Corresponding anionic (AP-10) and neutral (NP-10) copolymers with cholate pendants remained insignificant in controlling the aggregation process. Tyrosine fluorescence assays and Nile red fluorescence measurements demonstrate the role of hydrophobic interaction to explain the inhibitory potencies of CP-10. Furthermore, circular dichroism spectroscopic measurements were carried out to explore the secondary structural changes of insulin fibrils in the presence of cationic polymers with and without cholate moieties. Isothermal titration calorimetry measurements revealed the involvement of electrostatic polar interaction between the CA-based cationic polymer and insulin at different stages of fibrillation. Overall, this work demonstrates the efficacy of the CA-based cationic polymer in controlling the insulin aggregation process and provides a novel dimension to the studies on protein aggregation.

Zinc oxide nanoparticle interface moderation with tyrosine and tryptophan reverses the pro-amyloidogenic property of the particle

Zinc oxide nanoparticle with negative surface potential (ZnONP) enhances bovine insulin fibrillation. Here, we are exploring ZnONP with positive surface potential (ZnONP_Unc) and surface functionalized with tyrosine and tryptophan amino acids to observe the effects of surface potential and surface functional groups on the fibrillation. ZnONP_Unc, despite of inversed surface potential, enhances the insulin fibrillation with increase in the interface concentration at physiological pH. Whereas, the interface moderation with the amino acids mitigates the surface-mediated insulin fibrillation propensity. Additionally, the study indicates that the change in interfacial functional groups at ZnONP_Unc significantly reverses the interface-mediated destabilization of insulin conformation. The functional groups from the amino acids, like CO, N-H and aromatic functional groups, are anticipated to further stabilize the insulin conformation by forming hydrogen bond and van der Waals interactions with the key amyloidogenic sequences of insulin, A13-A20 from A-chain and B9-B20 from B-chain. Hence, the altered interaction profile, with change in interfacial functional groups, mitigates the interface-mediated insulin fibrillation and the ZnONP_Unc-/fibril-mediated cytotoxicity.

Amyloidogenicity of peptides targeting diabetes and obesity

Since the discovery of insulin, a century ago, the repertoire of therapeutic polypeptides targeting diabetes - and now also obesity - have increased substantially. The focus on quality has shifted from impure and unstable preparations of animal insulin to highly pure, homologous recombinant insulin, along with other peptide-based hormones and analogs such as amylin analogs (pramlintide, davalintide, cagrilintide), glucagon and glucagon-like peptide-1 receptor agonists (GLP-1, liraglutide, exenatide, semaglutide). Proper formulation, storage, manipulation and usage by professionals and patients are required in order to avoid agglomeration into high molecular weight products (HMWP), either amorphous or amyloid, which could result in potential loss of biological activity and short- or long-term immune reaction and silent inactivation. In this narrative review, we present perspective of the aggregation of therapeutic polypeptides used in diabetes and other metabolic diseases, covering the nature and mechanisms, analytical techniques, physical and chemical stability, strategies aimed to hamper the formation of HMWP, and perspectives on future biopharmaceutical developments.

Early detection of cutaneous complications of insulin therapy in type 1 and type 2 diabetes mellitus

BACKGROUND

Subcutaneous insulin therapy is associated with important injection site complications, which can influence insulin pharmacokinetics resulting in glycemic fluctuations above and below target levels for blood glucose.

OBJECTIVE

Our objective was to assess the prevalence and risk factors of cutaneous complications including insulin derived amyloidosis in insulin-injecting diabetes patients and to study the role of ultrasonography (in comparison to gel-assisted palpation) in early diagnosis of lipohypertrophy (LH).

METHODS

This was a cross-sectional study conducted at a tertiary care center in India, wherein 500 patients injecting insulin for ≥2 years were randomly enrolled and evaluated for the presence of cutaneous complications of insulin therapy through clinical examination, ultrasonography and punch biopsy of skin.

RESULTS

Clinical examination detected LH in 44.6% of patients. Ultrasonography diagnosed additional 13.4% of patients with LH which were missed on clinical examination. Incorrect rotation of sites (P < 0.001) and insulin syringe reusage for more than five times (P < 0.001) significantly increased the risk of LH. Skin biopsy was performed in 100 cases, out of which two patients showed apple green birefringence and its association with insulin was confirmed by positive staining with anti insulin antibody in these two patients.

CONCLUSION

Improper rotation of sites and reuse of needles were the leading causes of LH in Indian diabetic patients. Ultrasonography is more objective and reliable method of detecting LH. Insulin-derived amyloidosis may be a more common complication of insulin therapy than previously thought.

Monitoring the surface tension by the pendant drop technique for detection of insulin fibrillogenesis

Monitoring the aggregation of amyloid-prone proteins is critical for understanding the mechanism of amyloid fibril formation. Insulin, when dissolved in low pH buffer, has a surface tension of 61-64 mN m^-1, as measured by the pendant drop technique. Formation of insulin amyloid fibrils resulted in the increase of the surface tension values up to 71.2-73.5 mN m^-1. The kinetics of fibril formation and fibril morphology were validated by ThT fluorescence and AFM, respectively. The results demonstrate that monitoring the surface tension by the pendant drop technique is a valuable tool for the detection of insulin amyloid aggregation.

Prion-derived tetrapeptide stabilizes thermolabile insulin via conformational trapping

Unfolding followed by fibrillation of insulin even in the presence of various excipients grappled with restricted clinical application. Thus, there is an unmet need for better thermostable, nontoxic molecules to preserve bioactive insulin under varying physiochemical perturbations. In search of cross-amyloid inhibitors, prion-derived tetrapeptide library screening reveals a consensus V(X)YR motif for potential inhibition of insulin fibrillation. A tetrapeptide VYYR, isosequential to the β2-strand of prion, effectively suppresses heat- and storage-induced insulin fibrillation and maintains insulin in a thermostable bioactive form conferring adequate glycemic control in mouse models of diabetes and impedes insulin amyloidoma formation. Besides elucidating the critical insulin-IS1 interaction (R4 of IS1 to the N24 insulin B-chain) by nuclear magnetic resonance spectroscopy, we further demonstrated non-canonical dimer-mediated conformational trapping mechanism for insulin stabilization. In this study, structural characterization and preclinical validation introduce a class of tetrapeptide toward developing thermostable therapeutically relevant insulin formulations.

MALDI mass spectrometry imaging unravels organ and amyloid-type specific peptide signatures in pulmonary and gastrointestinal amyloidosis

PURPOSE

Amyloidosis is a disease group caused by pathological aggregation and deposition of peptides in diverse tissue sites. Recently, matrix-assisted laser desorption/ionization mass spectrometry imaging coupled with ion mobility separation (MALDI-IMS MSI) was introduced as a novel tool to identify and classify amyloidosis using single sections from formalin-fixed and paraffin-embedded cardiac biopsies. Here, we tested the hypothesis that MALDI-IMS MSI can be applied to lung and gastrointestinal specimens.

EXPERIMENTAL DESIGN

Forty six lung and 65 gastrointestinal biopsy and resection specimens with different types of amyloid were subjected to MALDI-IMS MSI. Ninety three specimens included tissue areas without amyloid as internal negative controls. Nine cases without amyloid served as additional negative controls.

RESULTS

Utilizing a peptide filter method and 21 known amyloid specific tryptic peptides we confirmed the applicability of a universal peptide signature with a sensitivity of 100% and a specificity of 100% for the detection of amyloid deposits in the lung and gastrointestinal tract. Additionally, the frequencies of individual m/z-values of the 21 tryptic marker peptides showed organ- and tissue-type specific differences.

CONCLUSIONS AND CLINICAL RELEVANCE

MALDI-IMS MSI adds a valuable analytical approach to diagnose and classify amyloid and the detection frequency of individual tryptic peptides is organ-/tissue-type specific.

Attenuation of subcutaneous insulin induced amyloid mass in vivo using Lumbrokinase and Serratiopeptidase

The protein misfolded structure called amyloids is related with extensive range of pathologies like local amyloidosis and neurodegenerative diseases. Several studies have reported the potential of insulin to generate local amyloidosis under certain state. Reports also showed that fibrils of insulin generated local amyloid mass due to continuous subcutaneous injection in mouse as well as rat. The present study was designed to examine the consequence of insulin fibril injections in rats, as well as the ability of enzymes, Lumbrokinase (LK) and Serratiopeptidase (SP) in diminishing this amyloid mass progression. The results showed that insulin fibrils generated amyloid masses in rats after subcutaneous injection for two weeks which was significantly condensed in size for the groups injected with insulin fibrils combined with LK or SP. At higher doses of LK and SP, the absence of amyloid structure was observed in histopathological studies. Light microscopy, polarized microscopy as well as Lumia live in vivo imaging system was used to analyze the results. In conclusion, the overall outcome of this study showed the anti-amyloid potential of enzyme LK and SP in the attenuation of local amyloidosis.

Amyloid formation of bovine insulin is retarded in moderately acidic pH and by addition of short-chain alcohols

Protein aggregation and amyloid formation are associated with multiple human diseases, but are also a problem in protein production. Understanding how aggregation can be modulated is therefore of importance in both medical and industrial contexts. We have used bovine insulin as a model protein to explore how amyloid formation is affected by buffer pH and by the addition of short-chain alcohols. We find that bovine insulin forms amyloid fibrils, albeit with different rates and resulting fibril morphologies, across a wide pH range (2–7). At pH 4.0, bovine insulin displayed relatively low aggregation propensity in combination with high solubility; this condition was therefore chosen as basis for further exploration of how bovine insulin’s native state can be stabilized in the presence of short-chain alcohols that are relevant because of their common use as eluents in industrial-scale chromatography purification. We found that ethanol and isopropanol are efficient modulators of bovine insulin aggregation, providing a three to four times retardation of the aggregation kinetics at 30–35% (vol/vol) concentration; we attribute this to the formation of oligomers, which we detected by AFM. We discuss this effect in terms of reduced solvent polarity and show, by circular dichroism recordings, that a concomitant change in α-helical packing of the insulin monomer occurs in ethanol. Our results extend current knowledge of how insulin aggregates, and may, although bovine insulin serves as a simplistic model, provide insights into how buffers and additives can be fine-tuned in industrial production of proteins in general and pharmaceutical insulin in particular.

Investigation of factors that cause insulin precipitation and/or amyloid formation in insulin formulations

Background

Multiple daily subcutaneous injections (MDSIs) are mainly used for formulating an insulin therapy for diabetic patients; however, they also cause insulin-derived amyloidosis (IDA) and lead to poor glycemic control. In addition, for the continuous subcutaneous insulin infusion system (CSII), precipitation frequently causes catheter occlusion and, if the precipitate in the formulations is amyloid, the injection of the insoluble amyloid into the subcutaneous tissue leads to IDA. The aim of this study was to conduct in vitro experiments and present a situation where insulin formulations cause precipitation and amyloid formation.

Methods

Humulin®R and NovoRapid® were used as model formulations for MDSIs and CSII, respectively. The generation of the precipitation was evaluated by measuring turbidity, and amyloid formation was evaluated by using Thioflavin T. Humulin®R was mixed with saline buffer solutions and glucose solutions to evaluate the effect of dilution. In addition, we created an experimental system to consider the effect of the time course of condition changes, and investigated the effects of insulin concentration, m-cresol existence, and pH change on the generation of the precipitate and amyloid in the formulation.

Results

In both the original and diluted formulations, physical stimulation resulted in the formation of a precipitate, which in most cases was an amyloid. The amyloid was likely to be formed at a near neutral pH. On the contrary, although a precipitate formed when the pH was decreased to near the isoelectric point, this precipitate was not an amyloid. Further decreases in pH resulted in the formation of amyloids, suggesting that both the positive and negative charged states of insulin tended to form amyloids. The formulation additive m-cresol suppressed amyloid formation. When additives were removed from the formulation, the amyloid-containing gel was formed in the field of substance exchange.

Conclusions

To consider changes in conditions that may occur for insulin formulations, the relationship between the formation of precipitates and amyloids was demonstrated in vitro by using insulin formulations. From the in vitro study, m-cresol was shown to have an inhibitory effect on amyloid formation.

Toxicity of insulin-derived amyloidosis: a case report

BACKGROUND

Insulin-derived amyloidosis is a skin-related complication of insulin therapy that interferes with insulin therapy. Although toxicities of in vitro-formed insulin amyloid fibrils have been well studied, the toxicity of insulin-derived amyloidosis remains to be clarified.

CASE PRESENTATION

A 58-year-old man with type 2 diabetes mellitus underwent a lower limb amputation due to diabetic gangrene. Several antibiotics including minocycline were administered for infection and sepsis. A hard mass at the insulin injection sites in the lower abdomen was discovered by chance four months later. Although no abnormal findings in the surface skin of the mass were observed, necrotic tissue was seen around the mass when a biopsy was performed. Histological and toxicity studies were performed for this patient and four other patients with abdominal masses at insulin injection sites. Histological and immunohistochemical studies showed that the masses had typical characteristics of amyloid deposits in all cases, whereas necrotic findings were seen adjacent to the amyloid deposit only in the case presented. Toxicity studies indicated that the amyloid tissue from the present case had significant cell toxicity compared to the control skin tissue or the amyloid tissues from the other four cases.

CONCLUSIONS

This report showed that toxic insulin-derived amyloidosis can occur. In addition, this report suggested that toxic insulin-derived amyloidosis may cause necrosis in the surrounding tissue. Although the toxic amyloid deposit of insulin-derived amyloidosis was found in only one patient, no structural differences between toxic and non-toxic deposits were seen on histological and immunohistochemical studies.

Extreme Adhesion Activity of Amyloid Fibrils Induces Subcutaneous Insulin Resistance

Insulin-derived amyloidoma, also called an insulin ball, is a skin-related complication of insulin therapy caused by repeated insulin injections at the same site, where native folded insulin changes into amyloid fibrils and forms a mass with a granulomatous reaction. Insulin-derived amyloidoma is a clinically important condition because of its association with subcutaneous insulin resistance, but the precise effect and mechanism of the insulin absorption impairment have not been clarified. We generated insulin-derived amyloidomas in mouse skin, with the amyloidomas large enough to perform insulin tolerance tests in the mass by repeated injections of highly concentrated insulin amyloid fibrils. We demonstrated that the insulin-derived amyloidomas inhibit insulin absorption. By simultaneous administration of insulin and insulin amyloid fibrils, we showed that this effect is due to the amyloid fibril itself in the absence of a granulomatous reaction. In vitro studies revealed that insulin amyloid fibrils have extremely strong adhesion to native human insulin and various insulin analogs. Furthermore, we showed that native insulin that had adhered to insulin amyloid forms amyloid fibrils at physiological pH. These results suggest that the extreme adhesion of insulin amyloid to native insulin is the main mechanism of impaired insulin absorption and amyloidoma growth.

Nanomedical Relevance of the Intermolecular Interaction Dynamics-Examples from Lysozymes and Insulins

Insulin and lysozyme share the common features of being prone to aggregate and having biomedical importance. Encapsulating lysozyme and insulin in micellar nanoparticles probably would prevent aggregation and facilitate oral drug delivery. Despite the vivid structural knowledge of lysozyme and insulin, the environment-dependent oligomerization (dimer, trimer, and multimer) and associated structural dynamics remain elusive. The knowledge of the intra- and intermolecular interaction profiles has cardinal importance for the design of encapsulation protocols. We have employed various biophysical methods such as NMR spectroscopy, X-ray crystallography, Thioflavin T fluorescence, and atomic force microscopy in conjugation with molecular modeling to improve the understanding of interaction dynamics during homo-oligomerization of lysozyme (human and hen egg) and insulin (porcine, human, and glargine). The results obtained depict the atomistic intra- and intermolecular interaction details of the homo-oligomerization and confirm the propensity to form fibrils. Taken together, the data accumulated and knowledge gained will further facilitate nanoparticle design and production with insulin or lysozyme-related protein encapsulation.

New Histologic Finding of Amyloid Insulin Bodies at an Insulin Injection Site in a Patient With Diabetes

Amyloidosis is a heterogeneous group of protein deposition diseases with more than 40 known clinical presentations. Localized amyloidosis occurs when the protein deposits exist in a singular location. Patients with diabetes mellitus who inject insulin at the same site can develop localized insulin-derived amyloidosis (AIns) at the injection site, which can be confused clinically with lipoma, lipohyperplasia, lipoatrophy, and fat necrosis. Histologic examination is performed to confirm localized AIns. We report a case of a patient with a long history of type 2 diabetes who presented with a subcutaneous mass in the abdomen at a preferred insulin injection site. Examination by light microscopy revealed diffuse deposition of eosinophilic material. Two of the tissue fragments contained numerous 30-40 μm spherical bodies within the eosinophilic material. The bodies had dark centers with peripheral eosinophilic material. Polarized sections stained with Congo red showed apple green birefringence, a characteristic of amyloid. Immunohistochemistry was positive for insulin antibodies in the dark spherules and the surrounding matrix. Proteomic analysis by mass spectrometry showed that the Congo red-positive material was insulin. Electron microscopy showed a background matrix consisting of nonbranching protein fibrils measuring 8.8-16.1 nm, consistent with amyloid; the spherules contained dark globular proteins in the center surrounded by nonbranching fibrillary proteins. Because these spherules were positive for insulin by immunohistochemistry and showed amyloid ultrastructurally, we refer to them as amyloid insulin bodies. The identification of AIns, specifically with amyloid insulin bodies, is important for diagnosis and treatment and may further our understanding of amyloidogenesis.

Cyanidin-3-rutinoside reduces insulin fibrillation and attenuates insulin fibrils-induced oxidative hemolysis of human erythrocytes

Insulin is able to form amyloid-like fibrils, a misfolding process by which insulin molecules interact with each other to form aggregates and pathological amyloid deposition. Inhibition of amyloid aggregation using natural products is proposed as a new strategy to prohibit the development of amyloid diseases. Herein, we demonstrated the inhibitory effect of cyanidin-3-rutinoside (C3R), a natural anthocyanin with multiple biological activities, against insulin amyloid fibrillation. The results showed that increased insulin concentration resulted in faster growth and higher amounts of insulin fibrils. C3R (10.6-170μM) concentration dependently decreased insulin fibril growth and increased the duration of lag time of insulin fibril formation. Moreover, C3R directly decreased the secondary structure transition from α-helix to β-sheet structure. C3R (0.31-5μM) attenuated insulin fibrils-induced oxidative hemolysis of human erythrocytes in a concentration-dependent manner. Moreover, C3R reduced insulin fibrils-induced erythrocyte membrane disruption through the inhibition of reactive oxygen species (ROS) generation. The findings also suggest that C3R reduced fibrils-induced membrane lipid peroxidation by maintaining the catalase activity and oxidized/reduced glutathione content (GSH/GSSH) in erythrocytes. These findings suggest that C3R may serve as a potential inhibitory agent against amyloid fibril formation and insulin fibrils-induced oxidative hemolysis.

MALDI Mass Spectrometry Imaging: A Novel Tool for the Identification and Classification of Amyloidosis

Amyloidosis is a group of diseases caused by extracellular accumulation of fibrillar polypeptide aggregates. So far, diagnosis is performed by Congo red staining of tissue sections in combination with polarization microscopy. Subsequent identification of the causative protein by immunohistochemistry harbors some difficulties regarding sensitivity and specificity. Mass spectrometry based approaches have been demonstrated to constitute a reliable method to supplement typing of amyloidosis, but still depend on Congo red staining. In the present study, we used matrix-assisted laser desorption/ionization mass spectrometry imaging coupled with ion mobility separation (MALDI-IMS MSI) to investigate amyloid deposits in formalin-fixed and paraffin-embedded tissue samples. Utilizing a novel peptide filter method, we found a universal peptide signature for amyloidoses. Furthermore, differences in the peptide composition of ALλ and ATTR amyloid were revealed and used to build a reliable classification model. Integrating the peptide filter in MALDI-IMS MSI analysis, we developed a bioinformatics workflow facilitating the identification and classification of amyloidosis in a less time and sample-consuming experimental setup. Our findings demonstrate also the feasibility to investigate the amyloid's protein composition, thus paving the way to establish classification models for the diverse types of amyloidoses and to shed further light on the complex process of amyloidogenesis.

Imaging characteristics of subcutaneous amyloid deposits in diabetic patients: the "insulin ball"

OBJECTIVE

The purpose of this study was to describe the imaging characteristics of subcutaneous amyloid deposits occurring at sites of insulin injection, commonly known as "insulin balls," in diabetic patients on ultrasound, CT, and MRI with pathologic correlation.

MATERIALS AND METHODS

We retrospectively reviewed the radiographic findings of 14 lesions in 9 patients diagnosed with subcutaneous amyloid deposits at our institution between 2005-2015. Three board-certified radiologists analyzed the following: (1) the shape, size, margin, morphologic characteristics, and blood flow on US using the color Doppler signal, (2) shape, size, margin, attenuation, and presence or absence of contrast enhancement on CT, and (3) shape, size, margin, signal intensity, and presence or absence of contrast enhancement on MRI.

RESULTS

All lesions showed ill-defined hypovascular subcutaneous nodules with irregular margins. The median diameter of lesions was 50.4 mm on US, 46.8 mm on CT, and 51.4 mm on MRI. The internal echogenicity of subcutaneous amyloid deposits was hypoechoic and heterogeneous on US. All lesions showed isodensity compared to muscle with irregular margins and minimal contrast enhancement on CT. Both T1- and T2-weighted MR images showed low signal intensity compared with subcutaneous fat. Normal diffusion and minimal contrast enhancement were seen.

CONCLUSIONS

Subcutaneous amyloid deposits which cause insulin resistance are typically ill-defined and heterogeneous hypovascular subcutaneous nodules with irregular margins on imaging that correspond to insulin injection sites. It is also characteristic that T2WI shows low intensity compared with fat on MRI, reflective of the amyloid content.

Ultrasonography Improves Glycemic Control by Detecting Insulin-Derived Localized Amyloidosis

We examined the feasibility of ultrasound diagnosis of insulin-derived localized amyloidosis (IDLA). In addition to ultrasound detectability and findings, the insulin absorption rate, insulin dosage and hemoglobin A1c (HbA1c) levels before and after shifting the insulin injection site were investigated for 22 cases of IDLA. The detectability of IDLA on ultrasound was 100%; 59.1% was palpable lumps and 40.9% was not palpable. The palpable type had lower echo intensity and were harder than the non-palpable type. Blood flow decreased in IDLA, especially in the palpable type. IDLA, especially the palpable type, had a low insulin absorption rate. HbA1c level and insulin dosage decreased after shifting the injection site. The palpable type had more insulin reduction than the non-palpable type. Characteristic ultrasound images of IDLA were acquired. As the non-palpable type could be identified by ultrasound, its diagnosis encourages changing the insulin injection site; hence, ultrasound diagnosis of IDLA can enhance insulin treatment.

Comparison of disaggregative effect of A-type EGCG dimer and EGCG monomer on the preformed bovine insulin amyloid fibrils

In the present study, the disruptive effects of epigallocatechin-3-gallate (EGCG) and A-type dimeric epigallocatechin-3-gallate (A-type EGCG dimer) on the preformed bovine insulin amyloid fibrils were studied by several biophysical methods including thioflavin-T (ThT) fluorescence assay, 1-anilinonaphthalene-8-sulfonic (ANS) fluorescence assay, Congo red (CR) binding assay, dynamic light scattering (DLS), transmission electron microscopy (TEM), Gel electrophoresis (SDS-PAGE) and Bradford assay. Our results demonstrated that A-type EGCG dimer showed significantly more potential disaggregative effects on the bovine insulin amyloid fibrils than EGCG. A-type EGCG dimer could not only dramatically promote the disaggregation of the preformed bovine insulin amyloid fibrils, but also restructure the amyloid fibrils into amorphous aggregates. While, EGCG could only shorten and thin the fibrils, but induce no small amorphous aggregates. Our present results provided additional evidence for the more potent disaggregation effects of dimeric polyphenols than monomeric polyphenols and suggested that A-type EGCG dimer seems to have potential application as an excellent anti-amyloidogenic agent.

Isolated insulin-derived amyloidoma of the breast

Isolated amyloidomas derived from insulin are extremely rare, and there is only one reported case to date of insulin-derived amyloidoma in the breast.We present the case of a 36-year-old woman reporting a lump in the right breast. It was clinically assessed as a probable fibroadenoma but was removed surgically given the size of the lesion. On histological analysis, the lesion had features consistent with amyloid. Further investigations showed the amyloid to be derived from insulin. The lump was removed in its entirety, and the patient made a full recovery.

Sural nerve injury in familial amyloid polyneuropathy: MR neurography vs clinicopathologic tools

OBJECTIVE

To detect and quantify lesions of the small-caliber sural nerve (SN) in symptomatic and asymptomatic transthyretin familial amyloid polyneuropathy (TTR-FAP) by high-resolution magnetic resonance neurography (MRN) in correlation with electrophysiologic and histopathologic findings.

METHODS

Twenty-five patients with TTR-FAP, 10 asymptomatic carriers of the mutated transthyretin gene (mutTTR), and 35 age- and sex-matched healthy controls were prospectively included in this cross-sectional case-control study. All participants underwent 3T MRN with high-structural resolution (fat-saturated, T2-weighted, and double-echo sequences). Total imaging time was ≈45 minutes per patient. Manual SN segmentation was performed from its origin at the sciatic nerve bifurcation to the lower leg with subsequent evaluation of quantitative microstructural and morphometric parameters. Additional time needed for postprocessing was ≈1.5 hours per participant. Detailed neurologic and electrophysiologic examinations were conducted in the TTR group.

RESULTS

T2 signal and proton spin density (ρ) reliably differentiated between TTR-FAP (198.0 ± 13.3, 429.6 ± 15.25), mutTTR carriers (137.0 ± 16.9, p = 0.0009; 354.7 ± 21.64, p = 0.0029), and healthy controls (90.0 ± 3.4, 258.2 ± 9.10; p < 0.0001). Marked differences between mutTTR carriers and controls were found for T2 signal (p = 0.0065) and ρ (p < 0.0001). T2 relaxation time was higher in patients with TTR-FAP only (p = 0.015 vs mutTTR carriers, p = 0.0432 vs controls). SN caliber was higher in patients with TTR-FAP vs controls and in mutTTR carriers vs controls (p < 0.0001). Amyloid deposits were histopathologically detectable in 10 of 14 SN specimens.

CONCLUSIONS

SN injury in TTR-FAP is detectable and quantifiable in vivo by MRN even in asymptomatic mutTTR carriers. Differences in SN T2 signal between controls and asymptomatic mutTTR carriers are derived mainly from an increase of ρ, which overcomes typical limitations of established diagnostic methods as a highly sensitive imaging biomarker for early detection of peripheral nerve lesions.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that MRN accurately identifies asymptomatic mutTTR carriers.

Amyloidosis: Insights from Proteomics

Amyloidoses are a spectrum of disorders caused by abnormal folding and extracellular deposition of proteins. The deposits lead to tissue damage and organ dysfunction, particularly in the heart, kidneys, and nerves. There are at least 30 different proteins that can cause amyloidosis. The clinical management depends entirely on the type of protein deposited, and thus on the underlying pathogenesis, and often requires high-risk therapeutic intervention. Application of mass spectrometry-based proteomic technologies for analysis of amyloid plaques has transformed the way amyloidosis is diagnosed and classified. Proteomic assays have been extensively used for clinical management of patients with amyloidosis, providing unprecedented diagnostic and biological information. They have shed light on the pathogenesis of different amyloid types and have led to identification of numerous new amyloid types, including ALECT2 amyloidosis, which is now recognized as one of the most common causes of systemic amyloidosis in North America.

Localized insulin amyloidosis with use of concentrated insulin: a potential complication

BACKGROUND

Insulin-derived amyloidosis is a rare form of amyloidosis composed of insulin fibrils. The pH and concentration of insulin are known to influence the conformational state of the insulin hormone, with an increasing concentration favouring a more complex conformation. Concentrated insulin delivers a large amount of insulin to a localized area, raising the possibility of inducing conformational changes, forming insulin fibrils and leading to localized insulin amyloidosis.

CASE REPORT

A middle-aged woman with long history of Type 2 diabetes mellitus, treated with concentrated human insulin (U-500 insulin) presented with nodular lesions at the site of her daily insulin injections. A punch biopsy of the nodules showed skin with dermal amyloidosis staining favourably with Congo Red stain. The amyloid tumours were resected and areas positive for Congo Red stain were sent for liquid chromatography tandem mass spectrometry, which showed a peptide profile consistent with amyloid insulin.

CONCLUSION

Concentrated insulin was first introduced in 1952, however, it is only over the last two decades that it has been used increasingly, in congruence with the increasing incidence of obesity and diabetes mellitus seen in the USA. Only a few cases of insulin amyloidosis at the site of injection have been described in literature. With the increase in the use of insulin, this complication seems to be occurring more frequently. This is the first case report of a person with diabetes mellitus who developed localized insulin amyloidosis with the use of concentrated insulin, and points towards a potential complication of developing insulin amyloidosis with the use of concentrated insulin.

Progressive insulin-derived amyloidosis in a patient with type 2 diabetes

Here, we report a case of insulin-derived amyloidosis in the lower abdomen. The mass continued to develop even after the patient ceased injecting insulin into the mass. Histological examination led to a diagnosis of insulin-derived amyloidosis. Excision is preferable in cases of insulin-derived amyloidosis if patient’s condition permits.

Insulin amyloid at injection sites of patients with diabetes

The formation of insulin amyloid can dramatically impact glycemic control in patients with diabetes, making it an important therapeutic consideration. In addition, the cost associated with the excess insulin required by patients with amyloid is estimated to be $3K per patient per year, which adds to the growing financial burden of this disease. Insulin amyloid has been observed with every mode of therapeutic insulin administration (infusion, injection and inhalation), and the number of reported cases has increased significantly since 2002. The new cases represent a much broader demographic, and include many patients who have used exclusively human insulin and human insulin analogs. The reason for the increase in case reports is unknown, but this review explores the possibility that changes in patient care, improved differential diagnosis and/or changes in insulin type and insulin delivery systems may be important factors. The goal of this review is to raise key questions that will inspire proactive measures to prevent, identify and treat insulin amyloid. Furthermore, this comprehensive examination of insulin amyloid can provide insight into important considerations for other injectable drugs that are prone to form amyloid deposits.

Interaction of partially denatured insulin with a DSPC floating lipid bilayer

The carefully controlled permeability of cellular membranes to biological molecules is key to life. In degenerative diseases associated with protein misfolding and aggregation, protein molecules or their aggregates are believed to permeate these barriers and threaten membrane integrity. We used neutron reflectivity to study the interaction of insulin, a model amyloidogenic protein, with a DSPC floating lipid bilayer. Structural changes consistent with protein partitioning to the membrane interior and adsorption to a gel phase model lipid bilayer were observed under conditions where the native fold of the protein is significantly destabilised. We propose that the perturbation of the membrane by misfolded proteins involves long term occupation of the membrane by these proteins, rather than transient perforation events.

Inhibition of insulin fibrillation by osmolytes: Mechanistic insights

We have studied here using a number of biophysical tools the effects of osmolytes, betaine, citrulline, proline and sorbitol which differ significantly in terms of their physical characteristics such as, charge distribution, polarity, H-bonding abilities etc, on the fibrillation of insulin. Among these, betaine, citrulline, and proline are very effective in decreasing the extent of fibrillation. Proline also causes a substantial delay in the onset of fibrillation in the concentration range (50–250 mM) whereas such an effect is seen for citrulline only at 250 mM, and in case of betaine this effect is not seen at all in the whole concentration range. The enthalpies of interaction at various stages of fibrillation process have suggested that the preferential exclusion of the osmolyte and its polar interaction with the protein are important in inhibition. The results indicate that the osmolytes are most effective when added prior to the elongation stage of fibrillation. These observations have significant biological implications, since insulin fibrillation is known to cause injection amyloidosis and our data may help in designing lead drug molecules and development of potential therapeutic strategies.

Amyloidoma secondary to insulin injection: Cytologic diagnosis and pitfalls

Amyloidomas are rare tumors composed of deposits of amyloid protein not associated with systemic amyloidosis. They can present as an initial manifestation of a systemic disease process or can be a completely localized phenomenon. We present a case of amyloidoma associated with insulin injection site found incidentally in an 80-year-old male with multiple co-morbidities who presented with diverticulitis associated bleeding. A subcutaneous abdominal mass was found on physical examination. Imaging revealed a 5 cm × 1.6 cm homogenous subcutaneous lesion. A fine-needle aspiration (FNA) and core biopsy were performed under ultrasound guidance to reveal amorphous material proven to be amyloidosis at insulin injection sites (AIns) type amyloid. The patient had no treatment for this lesion and has had his care triaged to his more serious health problems. This is the first case of AIns type amyloidoma associated with insulin injection site reported in cytology literature. We highlight the cytologic findings and diagnostic pitfalls. As the incidence of diabetes is increasing, cytopathologists may encounter this lesion more often on FNA.

MALDI-mass spectrometry imaging identifies vitronectin as a common constituent of amyloid deposits

Amyloids are pathological intra- and extracellular fibrillar aggregates of polypeptides with a cross-β-sheet structure and characteristic tinctorial properties. The amyloid deposits commonly enclose several non-fibrillar components of the extracellular matrix. Their potential to regulate the formation and aggregation process of amyloid fibrils is still poorly understood. For a better understanding of the role of the extracellular matrix in amyloidosis, it is essential to gain deeper insights into the composition of amyloid deposits. Here, we utilized matrix-assisted laser desorption and ionization mass spectrometry imaging to identify extracellular matrix compounds in amyloid deposits. Using this technique, we identified and determined the spatial distribution of vitronectin within AApoAI-, ALλ-, ATTR- and AIns amyloid deposits and, using immunohistochemistry, validated the spatial overlap of vitronectin with amyloids in 175 cases with diverse types of amyloid in several different tissues.