Insulin Molecule Research Articles

Management of Type 1 Diabetes in Children in the Outpatient Setting.

Management of Type 1 Diabetes in Children in the Outpatient Setting.

Intranasal delivery of insulin by self-emulsified nanoemulsion system: In vitro and in vivo studies

The main objective of this research was to develop a self-emulsified nanoemulsion (SEN) dosage form of insulin where insulin is loaded into the lipid phase of the nanoemulsion for enhanced absorption through intranasal delivery. When loaded into the lipid droplets (oil phase), insulin can be protected from enzymatic degradation, can penetrate through the mucus gel barrier in a comparatively effective manner and can be absorbed through transcellular permeation along with paracellular route. To incorporate lipophilicity to insulin molecule, Ins-SPC (Soy-L-α-phosphatidylcholine) complex was prepared by solid dispersion method to load insulin into the oil phase. The cytotoxicity of SPC and the developed nanoemulsions was tested on the human nasal epithelial cells in vitro. An optimized formulation with high loading of insulin and low in vitro cytotoxicity was developed and characterized. To predict the absorption of insulin through nasal mucosa in vivo by the nanoemulsion system, the insulin-loaded SEN along with controls was tested for the transport through human nasal epithelial cell monolayer in vitro. The insulin-loaded SEN significantly (p < 0.01) enhanced the permeation of insulin by three times as compared to the insulin solution. The in vivo absorption of insulin after intranasal delivery of the insulin-loaded SEN was evaluated in anesthetized rats. The results show that the Cmax (maximum plasma concentration) and the bioavailability (relative to the subcutaneous delivery) of the insulin-loaded SEN was 255.9 µU/ml and 68 %, respectively, while the intranasal delivery of the insulin solution resulted in only 5.8 µU/ml of Cmax and 5% of relative bioavailability. Intranasal delivery of 3.6 IU/kg insulin-loaded SEN decreased the plasma glucose level remarkably, achieving a maximum reduction of 70%, and the glucose reduction activity lasted for the whole experimental period of 4 h. Histological examination of the nasal mucosa showed no apparent signs of toxicity at the site of administration after single dose of the insulin-loaded SEN. These results demonstrate that the insulin-loaded SEN significantly enhanced insulin absorption through intranasal delivery, indicating that the developed nanoemulsion system offers a favorable approach for intranasal delivery of insulin.

Structural Investigations of Full-Length Insulin Receptor Dynamics and Signalling

Insulin regulates glucose homeostasis via binding and activation of the insulin receptor dimer at two distinct pairs of binding sites 1 and 2. Here, we present cryo-EM studies of full-length human insulin receptor (hIR) in an active state obtained at non-saturating, physiologically relevant insulin conditions. Insulin binds asymmetrically to the receptor under these conditions, occupying up to three of the four possible binding sites. Deletion analysis of the receptor together with site specific peptides and insulin analogs used in binding studies show that both sites 1 and 2 are required for high insulin affinity. We identify a homotypic interaction of the fibronectin type III domain (FnIII-3) of IR resulting in tight interaction of membrane proximal domains of the active, asymmetric receptor dimer. Our results show how insulin binding at two distinct types of sites disrupts the autoinhibited apo-IR dimer and stabilizes the active dimer. We propose an insulin binding and activation mechanism, which is sequential, exhibits negative cooperativity, and is based on asymmetry at physiological insulin concentrations with one to three insulin molecules activating IR.

Bioinformatics and Molecular Modeling of the Camel Insulin Receptor

Camels are well known for their high blood glucose content and marked glucose tolerance. In order to understand the glycemic control in camels the role of insulin receptor was investigated. The camel insulin receptor sequence, structure model, and domain content were compared with those of humans and other vertebrates. The results indicated 100% identity rate in old world camels, 99.7% identity rate with new world camels and 96% with humans. There was a high identity rate among insulin receptors in domestic animals (82.3–100%). Despite the conserved features of the insulin 1 binding site (the main functional insulin molecules), the second insulin-binding site in camel insulin receptors showed interesting differences. Most of the sequence differences between human and camel insulin receptors were concentrated in the insertion domains (ID), particularly the ID-β loop. ID-α′∼αCT′∼ID-β, which is important for insulin receptor signal transduction, showed a greater positive electrostatic potential in camels. Such differences might be associated with the noticed hyperglycemia and insulin resistance in camels by affecting the movement of the α-CT helix which lies between the IDs and signifcantly affects the main insulin molecules, lowering the affnity at insulin site 1 and by affecting the transmission of the insulin signal to the intracellular domain.

Unraveling the Gordian knot of insulin resistance in type 2 diabetes mellitus

&lt;abstract&gt; &lt;p&gt;β-cells play an important role in unraveling the Gordian knot of insulin resistance in type 2 diabetes. Firstly, a key feature of the etiology of type 2 diabetes, which appears in the prediabetic phase, is a reduction in the unsaturation index (number of cis carbon-carbon double bonds per 100 acyl chains of membrane phospholipids) compared to healthy controls, which leads to a lower rate of transmembrane glucose transport, and consequently causes reduced glucose effectiveness. Thus, the amount of glucose entering the β-cell via glucose transporter-2 reduces insulin production, leading to reduced insulin sensitivity. Secondly, after synthesis of monomer insulin, six monomer insulin molecules can join together in the presence of zinc ions. The mature hexamers are packed inside mature intracellular vesicles that are transported to the β-cell plasma membrane. Fusion of the intracellular vesicle membrane with the β-cell plasma membrane creates a fusion pore that allows expulsion of monomer insulin molecules into the blood circulation. The large dimensions of the monomer insulin molecule (30 Å wide and 35 Å high) require substantial flexibility of the vesicle membrane and the β-cell plasma membrane. Reduction in the unsaturation indexes leads to a lower rate of insulin transport into the blood circulation, which results in a further decrease in insulin sensitivity.&lt;/p&gt; &lt;p&gt;That brings us to a crucial point. The conceit behind the term “insulin resistance” is wrong. It suggests that cells do not respond well to insulin, but the fact is that this term ignores the essential reduction, compared to the plasma glucose concentration, in the amount of glucose entering the β-cell via glucose transporter-2, resulting in reduced insulin production. We now know that an increase in glucose effectiveness, powered by an increased unsaturation index, reframes fundamentally the mechanisms that participate in the glucose homeostasis during type 2 diabetes mellitus.&lt;/p&gt; &lt;/abstract&gt;

Experimental study on the interaction of insulin with apatitic calcium phosphates analogous to bone mineral: adsorption and release

The present work investigated the interaction of human insulin with synthesized poorly crystalline apatitic calcium phosphates containing simultaneously HPO42- and CO32- ions in various amount. The adsorption kinetics is very fast, while the release kinetics is generally slow. The chemical composition of apatite has an influence on both the adsorption and release processes. The experimental results show that the percentage of insulin adsorption and release decreased with the increase of the content of carbonate. The equilibrium adsorption data are fitted into Langmuir, Freundlich, Elovich, Temkin, and Dubinin–Radushkevich isotherms. The Langmuir model is best suited with a maximum monolayer adsorption capacity of 33.20 and 25.08 mg/g at 310 K corresponding to the carbonated and octocalcium phosphate apatite respectively. Isotherms parameters have revealed that the adsorption of insulin on these apatites is a feasible, spontaneous, and exothermic process. Fourier-transforms infrared confirm the fixation of insulin on non-carbonated and carbonated apatite. The adsorption and release of insulin molecules can be well described as an ions exchange-reaction between species in the hydrated layer of apatite and other species in solution. All of these results suggested that apatitic calcium phosphates can be used as systems for insulin delivery.

Advancements and future directions in research of the roles of insulin in amyloid diseases

Amyloid diseases, such as type 2 diabetes, Alzheimer's disease and Parkinson's disease are characterized by amyloid aggregates. Insulin is released from the pancreas, and it is known that insulin downstream signaling molecules are located majorly in the regions of cortex and hippocampus. Therefore, insulin plays crucial roles not only in the pancreas, but also in the brain. Recent studies have focused on the role of insulin in amyloid diseases. This review demonstrates the recent studies in which insulin affects amyloid aggregation. Specifically, molecular modeling studies provide insights into the molecular mechanisms of the effects of insulin in amyloid aggregates. Still, experimental studies are required to provide insights into the kinetics effects. This review opens new avenues for future studies on insulin molecules and amyloid aggregation.

Kinetics of Phenol Escape from the Insulin R6 Hexamer.

Therapeutic preparations of insulin often contain phenolic molecules, which can impact both pharmacokinetics and shelf life. Thus, understanding the interactions of insulin and phenolic molecules can aid in designing improved therapeutics. In this study, we use molecular dynamics to investigate phenol release from the insulin hexamer. Leveraging recent advances in methods for analyzing molecular dynamics data, we expand on existing simulation studies to identify and quantitatively characterize six phenol binding/unbinding pathways for wild-type and A10 Ile → Val and B13 Glu → Gln mutant insulins. A number of these pathways involve large-scale opening of the primary escape channel, suggesting that the hexamer is much more dynamic than previously appreciated. We show that phenol unbinding is a multipathway process, with no single pathway representing more than 50% of the reactive current and all pathways representing at least 10%. We use the mutant simulations to show how the contributions of specific pathways can be rationally manipulated. Predicting the net effects of mutations is more challenging because the kinetics depend on all of the pathways, demanding quantitatively accurate simulations and experiments.

Trends in Insulin Types and Devices Used by Adults With Type 2 Diabetes in the United States, 2016 to 2020

Despite rising costs and public scrutiny devoted to insulin, less is known regarding recent trends in its ambulatory use in the United States. To characterize trends in ambulatory insulin use, overall and based on insulin characteristics, among adults with type 2 diabetes in the United States from January 1, 2016, through December 31, 2020. This serial cross-sectional study included patients whose data were collected in IQVIA's National Disease and Therapeutic Index (NDTI), a 2-stage, all-payer, nationally representative audit of outpatient care. Approximately 4800 physicians each calendar quarter completed a form for 2 consecutive days regarding visits for each of their patients, including diagnoses, treatments, and demographic information. Data were collected from January 2016 through December 2020. Ambulatory use of insulin. Nationally representative projections for ambulatory use of insulin (ie, treatment visits), overall and aggregated by insulin molecule (insulins regular, neutral protamine Hagedorn [NPH], lispro, glulisine, glargine, detemir, degludec, and aspart), delivery devices (vials/syringes or pens), therapeutic class (short-acting, rapid-acting, long-acting, intermediate-acting, and premixed insulin), insulin type (human, analog, and biosimilar), and date of approval (newer: before 2010; and older: after 2010). There were 27 860 691 insulin treatment visits between 2016 and 2020. Among all patient encounters that indicated use of insulin in 2020, 1 989 154 (43.9%) were among those aged 60 to 74 years; 2 372 629 (52.4%) among men; 2 646 247 (58.4%) among White patients; 811 639 (17.9%) among Black patients; and 701 912 (15.5%) among Hispanic patients. Insulin glargine was the most frequently used insulin from 2016 to 2020, accounting for approximately half of treatment visits (eg, 2020: 2.6 of 4.9 million visits; 95% CI, 2.1-3.1 million). Among insulin classes, long-acting insulin accounted for approximately two-thirds of treatment visits during this period (eg, 2020: 3.7 million visits; 95% CI, 3.0-4.4 million). Treatment visits for insulin pens increased from 36.1% in 2016 (2.2 of 6.0 million visits; 95% CI, 1.7-2.7 million) to 58.7% in 2020 (2.9 million visits; 95% CI, 2.3-3.5 million), while use of insulin vials/syringes declined in parallel. Analog insulin use predominated and accounted for more than 80% of total treatment visits across all years (eg, 2020: 4.3 million visits; 95% CI, 3.4-5.1 million). Newer insulins were increasingly used, from 18.1% of total treatment visits in 2016 (1.1 million visits; 95% CI, 0.8-1.4 million) to 40.9% in 2020 (2.0 million visits; 95% CI, 1.5-2.5 million). The use of biosimilar insulin, which was first approved in 2015, increased from 2.6% in 2017 (0.1 of 5.3 million visits; 95% CI, 0.04-0.2 million) to 8.2% in 2020 (0.4 million visits; 95% CI, 0.2-0.6 million) of total insulin treatment visits. The total number of insulin treatment visits declined from a peak of 6.0 million visits in 2016 to a nadir of 4.9 million visits in 2020 (approximately 18% decline). In this study, ambulatory insulin use in the United States during the past 5 years remained dominated by the use of insulin analogs and insulin pen delivery devices, with increasing uptake of newer products as they have been brought to market.

A pharmacological approach assessing the role of mast cells in insulin infusion site inflammation.

Background Extending the lifespan of subcutaneous insulin administration sets and infusion pumps requires overcoming unreliable insulin delivery induced by dermal reactions. All commercially available insulin formulations contain insulin phenolic preservatives (IPP), which stabilize the insulin molecule but result in unwanted cell and tissue toxicity. Mast cells, which are the first line of defense once the epithelium is breached, are particularly abundant beneath the skin surface. Thus, we hypothesize a sequence of events initiated by device insertion that activates skin mast cells (MC) that subsequently trigger neutrophil and monocyte/macrophage recruitment. The ensuing inflammatory response compromises effective insulin infusion therapy. Methods We employed a non-genetic, pharmacological approach to MC membrane stabilization using Cromolyn sodium (CS), which inhibits MC degranulation. These studies were conducted in our modified air pouch mouse model using non-diabetic and streptozotocin induced diabetic mice. We evaluated the impact of systemic CS through intraperitoneal injections, as well as the impact of local CS through co-infusion, on infusion catheter insertion and IPP-induced inflammation. Results CS at a concentration of 50mg/kg minimized inflammation triggered in response to insulin phenolic preservatives present in standard insulin formulations. The resultant degree of tissue inflammation was comparable to that observed with saline injections. Conclusion Targeting MC has the potential to extend the longevity of insulin infusion sets by mitigating the inflammatory response. Future studies should be directed at employing other MC models, such as newer Cre/loxP mouse strains, to confirm the sentinel role of MC in insulin infusion therapy.

Robust adaptation of PKC ζ-IRS1 insulin signaling pathways through integral feedback control

Insulin signaling pathways in muscle tissue play a major role in maintaining glucose homeostasis. Dysregulation in these pathways results in the onset of serious metabolic disorders like type 2 diabetes. Robustness is an essential characteristic of insulin signaling pathways that ensures reliable signal transduction in the presence of perturbations as a result of several feedback mechanisms. Integral control, according to control engineering, provides reliable setpoint tracking and disturbance rejection. The presence of negative feedback and integrating process is crucial for biological processes to achieve integral control. The existence of an integral controller leads to the rejection of perturbations which resulted in the robust regulation of biochemical entities within acceptable levels. In the present in silico research work, the presence of integral control in the protein kinase C ζ - insulin receptor substrate-1 (PKC ζ-IRS1) pathway is identified, verified mathematically and model is simulated in Cell Designer. The data is exported to Minitab software and robustness analysis is carried out statistically using the Mann-Whitney test. The p-value of the results obtained with given parameters perturbed by ±1% is greater than the significance level of 0.05 (0.2132 for 1% error in k7(rate constant of IRS1 phosphorylation), 0.2096 for −1% error in k7, 0.9037 for both ±1% error in insulin and 0.9037 for ±1% error in k1(association rate constant of the first molecule of insulin to bind the insulin receptor), indicated that our hypothesis is proved The results satisfactorily indicate that even when perturbations are present, glucose homeostasis in muscle tissue is robust due to the presence of integral regulation in the PKC ζ-IRS1 insulin signaling pathways. In this paper, we have analysed the findings from the framework of robust control theory, which has allowed us to examine that how PKC ζ-IRS1 insulin signaling pathways produces desired output in presence of perturbations.

Molecular and pharmacological characterization of insulin icodec: a new basal insulin analog designed for once-weekly dosing

IntroductionInsulin icodec is a novel, long-acting insulin analog designed to cover basal insulin requirements with once-weekly subcutaneous administration. Here we describe the molecular engineering and the biological and pharmacological properties...

Type 1 diabetes glycemic management: Insulin therapy, glucose monitoring, and automation.

Despite innovations in insulin therapy since its discovery, most patients living with type 1 diabetes do not achieve sufficient glycemic control to prevent complications, and they experience hypoglycemia, weight gain, and major self-care burden. Promising pharmacological advances in insulin therapy include the refinement of extremely rapid insulin analogs, alternate insulin-delivery routes, liver-selective insulins, add-on drugs that enhance insulin effect, and glucose-responsive insulin molecules. The greatest future impact will come from combining these pharmacological solutions with existing automated insulin delivery methods that integrate insulin pumps and glucose sensors. These systems will use algorithms enhanced by machine learning, supplemented by technologies that include activity monitors and sensors for other key metabolites such as ketones. The future challenges facing clinicians and researchers will be those of access and broad clinical implementation.

100 years of insulin: celebrating the past, present and future of diabetes therapy.

The year 2021 marks the centennial of Banting and Best's landmark description of the discovery of insulin. This discovery and insulin's rapid clinical deployment effectively transformed type 1 diabetes from a fatal diagnosis into a medically manageable chronic condition. In this Review, we describe key accomplishments leading to and building on this momentous occasion in medical history, including advancements in our understanding of the role of insulin in diabetes pathophysiology, the molecular characterization of insulin and the clinical use of insulin. Achievements are also viewed through the lens of patients impacted by insulin therapy and the evolution of insulin pharmacokinetics and delivery over the past 100 years. Finally, we reflect on the future of insulin therapy and diabetes treatment, as well as challenges to be addressed moving forward, so that the full potential of this transformative discovery may be realized.

Molecular dynamic and in vitro evaluation of chitosan/tripolyphosphate nanoparticles as an insulin delivery system at two different pH values

Understanding the atomic interaction mechanism between chitosan and insulin at different pH levels is essential in the design of chitosan-based drug-delivery systems. In the present study, insulin-loaded nanoparticles were prepared via ionic gelation of tripolyphosphate (TPP) and chitosan with 76 ± 5.5% encapsulation efficiency. Our results showed that the nanoparticles were spherical with a size of 254 nm. Furthermore, the in vitro release profile of insulin was evaluated for two different pH levels. The release of insulin from nanoparticles after 48 h at pH 4.0 was 92%, compared to 56% at pH 7.4. The kinetics of the release were best fitted by the Weibull equation, which described a burst release in the first five hours followed by a sustained insulin release for up to 48 h. Moreover, we designed a long single chain chitosan (128 kDa)/TPP nanoparticles in real size for the first time and studied the system behavior in acidic and neutral environments using molecular dynamic simulation for 40 nanoseconds (ns). Our results showed that chitosan chains opened more with higher root-mean-square deviation (RMSD) values at pH 4.0 than at pH 7.4. Also, RMSD plots for insulin and TPP molecules showed that insulin molecules diffused away from chitosan chains, and that TPP were randomly dispersed further away from the chitosan chain in an acidic medium than in a neutral one. The in silico studies were in agreement with our in vitro data. Thus self-assembled chitosan/TPP nanoparticles show promise as a means to release protein drugs in acidic environments. Communicated by Ramaswamy H. Sarma

203-OR: Measurement of Intact Insulin by Mass Spectrometry Identifies Nonalcoholic Fatty Liver Disease (NAFLD)

Patients with NAFLD are characterized by insulin resistance (IR) and hyperinsulinism. However, prior studies have been unable to predict NAFLD based on IR measurements. The aim of this study was to explore the application of a newly validated measurement of intact insulin by mass spectrometry to predict NAFLD in patients without diabetes. Ninety-eight patients were recruited and underwent: a 2-hour OGTT with measurements of insulin every 30 min, and a liver magnetic resonance spectroscopy (1H-MRS) to measure liver fat and diagnose NAFLD. A mass spectrometry method was used to measure intact molecules of insulin. A total of 62 patients had NAFLD (48±11 yr, 66% male, BMI: 34.4±4.6kg/m2, A1c: 5.8±0.4%); and 36 did not have NAFLD (52±12 yr, 56% male, BMI: 30.5±6.8kg/m2, A1c: 5.5±0.4%). Fasting insulin levels were higher in NAFLD patients (17±10 vs. 7±3 μU/ml, p&amp;lt;0.001), but showed similar excursions during the OGTT (120 min incremental AUC: 7.4 [4.4-14.5] vs. 5.7 [4.2-8.9], p=0.22). Fasting intact insulin measurements had an AUROC of 0.90 (0.84-0.96) to predict NAFLD. This was significantly better than measuring insulin by radioimmunoassay (RIA) (AUC 0.80 [0.71-0.89], p=0.007). Using a cut-off of 10.5 μU/ml, we observed a sensitivity, specificity, PPV, and NPV of 92% (87-98%), 71% (62-80%), 79% (71-87%), and 89% (83-95%), respectively. Intact fasting insulin was better than other clinical variables (e.g., ALT, AST, triglycerides, HDL, glucose, A1c, and BMI) to predict NAFLD. When combined with ALT (intact insulin x ALT), it detected NAFLD with AUC 0.94 (0.89-0.99) and PPV and NPV of 93 and 88%, respectively. This newly described approach was significantly better than previously validated non-invasive scores such as NAFLD-LFS (p=0.009), HIS (p&amp;lt;0.001) and TyG index (p=0.039). Conclusions: In patients without diabetes, accurate measurement of fasting intact insulin levels by mass spectrometry constitutes an easy and non-invasive strategy to predict presence of NAFLD. Disclosure F. Bril: None. M. J. Mcphaul: Employee; Self; Quest Diagnostics. S. Kalavalapalli: None. R. Lomonaco: None. D. Barb: None. E. Godinez: None. K. Cusi: None. Funding The Obesity Society; University of Florida

Minimal and Maximal Models to Quantitate Glucose Metabolism: Tools to Measure, to Simulate and to Run in Silico Clinical Trials.

Several models have been proposed to describe the glucose system at whole-body, organ/tissue and cellular level, designed to measure non-accessible parameters (minimal models), to simulate system behavior and run in silico clinical trials (maximal models). Here, we will review the authors' work, by putting it into a concise historical background. We will discuss first the parametric portrait provided by the oral minimal models-building on the classical intravenous glucose tolerance test minimal models-to measure otherwise non-accessible key parameters like insulin sensitivity and beta-cell responsivity from a physiological oral test, the mixed meal or the oral glucose tolerance tests, and what can be gained by adding a tracer to the oral glucose dose. These models were used in various pathophysiological studies, which we will briefly review. A deeper understanding of insulin sensitivity can be gained by measuring insulin action in the skeletal muscle. This requires the use of isotopic tracers: both the classical multiple-tracer dilution and the positron emission tomography techniques are discussed, which quantitate the effect of insulin on the individual steps of glucose metabolism, that is, bidirectional transport plasma-interstitium, and phosphorylation. Finally, we will present a cellular model of insulin secretion that, using a multiscale modeling approach, highlights the relations between minimal model indices and subcellular secretory events. In terms of maximal models, we will move from a parametric to a flux portrait of the system by discussing the triple tracer meal protocol implemented with the tracer-to-tracee clamp technique. This allows to arrive at quasi-model independent measurement of glucose rate of appearance (Ra), endogenous glucose production (EGP), and glucose rate of disappearance (Rd). Both the fast absorbing simple carbs and the slow absorbing complex carbs are discussed. This rich data base has allowed us to build the UVA/Padova Type 1 diabetes and the Padova Type 2 diabetes large scale simulators. In particular, the UVA/Padova Type 1 simulator proved to be a very useful tool to safely and effectively test in silico closed-loop control algorithms for an artificial pancreas (AP). This was the first and unique simulator of the glucose system accepted by the U.S. Food and Drug Administration as a substitute to animal trials for in silico testing AP algorithms. Recent uses of the simulator have looked at glucose sensors for non-adjunctive use and new insulin molecules.

Monitoring Silver(I)-Insulin Complexes with Electrospray Ionization Quadrupole Ion Trap Mass Spectrometry.

Ag(I)-insulin complex formation was investigated using electrospray quadrupole ion trap mass spectrometry (ESI-QIT-MS), and Ag(I) ion binding to an insulin molecule was evaluated. The Ag(I) binding ratios were measured in the range of pH 3-8. The highest binding ratio of the Ag(I) ions was obtained at pH 7. Spectrometric titration was carried out at varied molar ratios of Ag(I) ions to insulin from 20/1 to 250/1. It was observed that four Ag(I) ions were bound effectively to an insulin molecule to form Ag(I)1-4-insulin complexes. The formation equilibrium constants of Ag(I)1-4-insulin complexes were calculated from the ESI-QIT-MS peak intensities. The equilibrium constants were found as Kf1 = (2.92 ± 0.18) × 104 M-1, Kf2 = (1.03 ± 0.07) × 104 M-1, Kf3 = (6.67 ± 0.46) × 103 M-1, and Kf4 = (2.00 ± 0.16) × 103 M-1. The tandem MS/MS spectroscopies were studied to evaluate the stability of the Ag(I) complexes. The different flow rates with nano-ESI were performed to determine the binding of Ag(I) ions in solution or gas phase. In conclusion, it was observed that the Ag(I) ion forms stable Ag(I)1-4-complexes with high formation equilibrium constants.

Phenolic Preservative Removal from Commercial Insulin Formulations Reduces Tissue Inflammation while Maintaining Euglycemia.

Background: Exogenous insulin therapy requires stabilization of the insulin molecule, which is achieved through the use of excipients (e.g., phenolic preservatives (PP)) that provide protein stability, sterility and prolong insulin shelf life. However, our laboratory recently reported that PP, (e.g., m-creosol and phenol) are also cytotoxic, inducing inflammation and fibrosis. Optimizing PP levels through filtration would balance the need for insulin preservation with PP-induced inflammation. Method: Zeolite Y (Z-Y), a size-exclusion-based resin, was employed to remove PP from commercial insulin formulations (Humalog) before infusion. Results: PP removal significantly decreased cell toxicity in vitro and inflammation in vivo. Infusion site histological analysis after a 3 day study demonstrated that leukocyte accumulation increased with nonfiltered preparations but decreased after filtration. Additional studies demonstrated that a Z-Y fabricated filter effectively removed excess PP such that the filtered insulin solution achieved equivalent glycemic control in diabetic mice when compared to nonfiltered insulin. Conclusion: This approach represents the proof of concept that using Z-Y for in-line PP removal assists in lowering inflammation at the site of insulin infusion and thus could lead to extending the functional lifespan of insulin infusion sets in vivo.

Systematic stability testing of insulins as representative biopharmaceuticals using ATR FTIR-spectroscopy with focus on quality assurance.

.Significance: Bioactive proteins represent the most important component class in biopharmaceutical products for therapeutic applications. Their production is most often biotechnologically realized by genetically engineered microorganisms. For the quality assurance of insulins as representatives of life-saving pharmaceuticals, analytical methods are required that allow more than total protein quantification in vials or batches. Chemical and physical factors such as unstable temperatures or shear rate exposure under storage can lead to misfolding, nucleation, and subsequent fibril forming of the insulins. The assumption is valid that these processes go parallel with a decrease in bioactivity.Aim: Infrared (IR) spectroscopy has been successfully utilized for secondary structure analysis in cases of protein misfolding and fibril formation.Approach: A reliable method for the quantification of the secondary structure changes has been developed using insulin dry-film Fourier-transform IR spectroscopy in combination with the attenuated total reflection (ATR) technique and subsequent data analyses such as band-shift determination, spectral band deconvolution, and principal component analysis.Results: A systematic study of insulin spectra was carried out on model insulin specimens, available either as original formulations or as hormones purified by ultrafiltration. Insulin specimens were stored at different temperatures, i.e., 0°C, 20°C, and 37°C, respectively, for up to three months. Weekly ATR-measurements allowed the monitoring of hormone secondary structure changes, which are supposed to be negatively correlated with insulin bioactivity.Conclusions: It could be shown that IR-ATR spectroscopy offers a fast and reliable analytical method for the determination of secondary structural changes within insulin molecules, as available in pharmaceutical insulin formulations and therefore challenges internationally established measurement techniques for quality control regarding time, costs, and effort of analysis.