Insulin's 85th anniversary--An enduring medical miracle

Formation of Protamine and Zn-Insulin Assembly: Exploring Biophysical Consequences

The insulin-protamine interaction is at the core of the mode of action in many insulin formulations (Zn + insulin + protamine) and to treat diabetes, in which protamine is added to the stable form of hexameric insulin (Zn-insulin). However, due to the unavailability of quantitative data and a high-resolution structure, the binding mechanism of the insulin-protamine complex remains unknown. In this study, it was observed that Zn-insulin experiences destabilization as observed by the loss of secondary structure in circular dichroism (CD), and reduction in thermal stability in melting study, upon protamine binding. In isothermal titration calorimetry (ITC), it was found that the interactions were mostly enthalpically driven. This is in line with the positive ΔC _m value (+880 cal mol^-1), indicating the role of hydrophilic interactions in the complex formation, with the exposure of hydrophobic residues to the solvent, which was firmly supported by the 8-anilino-1-naphthalene sulfonate (ANS) binding study. The stoichiometry (N) value in ITC suggests the multiple insulin molecules binding to the protamine chain, which is consistent with the picture of the condensation of insulin in the presence of protamine. Atomic force microscopy (AFM) suggested the formation of a heterogeneous Zn-insulin-protamine complex. In fluorescence, Zn-insulin experiences strong Tyr quenching, suggesting that the location of the protamine-binding site is near Tyr, which is also supported by the molecular docking study. Since Tyr is critical in the stabilization of insulin self-assembly, its interaction with protamine may impair insulin's self-association ability and thermodynamic stability while at the same time promoting its flexible conformation desired for better biological activity.

Progress in Simulation Studies of Insulin Structure and Function

Insulin is a peptide hormone known for chiefly regulating glucose level in blood among several other metabolic processes. Insulin remains the most effective drug for treating diabetes mellitus. Insulin is synthesized in the pancreatic β-cells where it exists in a compact hexameric architecture although its biologically active form is monomeric. Insulin exhibits a sequence of conformational variations during the transition from the hexamer state to its biologically-active monomer state. The structural transitions and the mechanism of action of insulin have been investigated using several experimental and computational methods. This review primarily highlights the contributions of molecular dynamics (MD) simulations in elucidating the atomic-level details of conformational dynamics in insulin, where the structure of the hormone has been probed as a monomer, dimer, and hexamer. The effect of solvent, pH, temperature, and pressure have been probed at the microscopic scale. Given the focus of this review on the structure of the hormone, simulation studies involving interactions between the hormone and its receptor are only briefly highlighted, and studies on other related peptides (e.g., insulin-like growth factors) are not discussed. However, the review highlights conformational dynamics underlying the activities of reported insulin analogs and mimetics. The future prospects for computational methods in developing promising synthetic insulin analogs are also briefly highlighted.

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.

Living with Insulin: The story of insulin from people with diabetes

The history of insulin is rightly considered one of the most beautiful stories in medicine which goes even further than the extraordinary result of tens of millions of lives saved. Without a doubt, it constitutes a major achievement for medical science which, especially in the last 50 years, has led to an impressive acceleration in the succession of new treatment opportunities. We are going to describe the history of insulin therapy, the history we lived from two different angles as people living with type 1 diabetes, and obviously also as diabetologists, but as diabetologists with diabetes. Without a doubt, insulin and his story constitutes a major achievement for medical science which has led to an impressive acceleration in the succession of new treatment opportunities. Care opportunities that have not only allowed fundamental improvements in outcomes, but have also and above all impacted the quality of life of people with diabetes. Summarizing one hundred years of insulin is no simple endeavor. In our view, it would be easier, and probably more befitting, to focus on the last 50 years, namely the period we have lived closely and personally together with insulin. More to the point, these last 50 years have witnessed a dramatic acceleration of research and innovation. In our opinion, it is precisely the innovations in insulin therapy introduced from the last decades that fully justify the description of events in this incredible period as "the miracle of insulin". We'll describe how the most important innovations introduced in the last decades had impact on what we have nowadays, as patients and diabetologits: today, we can finally adapt insulin therapy to the patient's life or lifestyle, reversing what was the perception of patients until 20 years, when insulin was considered, by the most, as an obstacle, which seemed insurmountable to some, to a free and unconstrained life.

A cross-species analysis of systemic mediators of repair and complex tissue regeneration

Regeneration is an elegant and complex process informed by both local and long-range signals. Many current studies on regeneration are largely limited to investigations of local modulators within a canonical cohort of model organisms. Enhanced genetic tools increasingly enable precise temporal and spatial perturbations within these model regenerators, and these have primarily been applied to cells within the local injury site. Meanwhile, many aspects of broader spatial regulators of regeneration have not yet been examined with the same level of scrutiny. Recent studies have shed important insight into the significant effects of environmental cues and circulating factors on the regenerative process. These observations highlight that consideration of more systemic and possibly more broadly acting cues will also be critical to fully understand complex tissue regeneration. In this review, we explore the ways in which systemic cues and circulating factors affect the initiation of regeneration, the regenerative process, and its outcome. As this is a broad topic, we conceptually divide the factors based on their initial input as either external cues (for example, starvation and light/dark cycle) or internal cues (for example, hormones); however, all of these inputs ultimately lead to internal responses. We consider studies performed in a diverse set of organisms, including vertebrates and invertebrates. Through analysis of systemic mediators of regeneration, we argue that increased investigation of these "systemic factors" could reveal novel insights that may pave the way for a diverse set of therapeutic avenues.

Design a synthetic glucose receptor using computational intelligence approach

The synthetic glucose receptors help to develop glucose sensors and alternative insulin therapies. Designing a glucose recognition molecule in an aqueous system remains a considerable challenge. Therefore, In-silico molecular screening hypothesis is proposed to overcome the difficulties found during the modeling of a molecule. The small organic compounds from compound databases are screened for glucose receptor modeling. Thereafter, the different computational models are designed that mimic natural glucose receptors based on screened compounds. The orientation and binding of glucose molecules within the developed receptor are predicted through the molecular interaction approach. The modeled receptors and receptor-glucose complex structures are used for geometry optimization and molecular dynamics computation. The docking results reveal that ZINC82047919, ZINC238094340, and ZINC238519600 compounds-based models provide better interactions with glucose and its orientation within the receptor cavity. The molecular dynamics simulation results showed that the receptor designed using compound ZINC238094340 is unable to hold the glucose and undergo significant conformation changes during simulation process. The receptor designed from ZINC238094340 and ZINC238519600 compounds is utilized as a reference glucose binding receptor in this study. The proposed computational approach is able to develop a novel glucose receptor and other glucose relative sugar molecules.

Glucose-responsive insulin by molecular and physical design

The concept of a glucose-responsive insulin (GRI) has been a recent objective of diabetes technology. The idea behind the GRI is to create a therapeutic that modulates its potency, concentration or dosing relative to a patient's dynamic glucose concentration, thereby approximating aspects of a normally functioning pancreas. From the perspective of the medicinal chemist, the GRI is also important as a generalized model of a potentially new generation of therapeutics that adjust potency in response to a critical therapeutic marker. The aim of this Perspective is to highlight emerging concepts, including mathematical modelling and the molecular engineering of insulin itself and its potency, towards a viable GRI. We briefly outline some of the most important recent progress toward this goal and also provide a forward-looking viewpoint, which asks if there are new approaches that could spur innovation in this area as well as to encourage synthetic chemists and chemical engineers to address the challenges and promises offered by this therapeutic approach.

Towards Point-of-Care Insulin Detection

Good glucose management through an insulin dose regime based on the metabolism of glucose helps millions of people worldwide manage their diabetes. Since Banting and Best extracted insulin, glucose management has improved due to the introduction of insulin analogues that act from 30 minutes to 28 days, improved insulin dose regimes, and portable glucose meters, with a current focus on alternative sampling sites that are less invasive. However, a piece of the puzzle is still missing-the ability to measure insulin directly in a Point-of-Care device. The ability to measure both glucose and insulin concurrently will enable better glucose control by providing an improved estimate for insulin sensitivity, minimizing variability in control, and maximizing safety from hypoglycaemia. However, direct detection of free insulin has provided a challenge due to the size of the molecule, the low concentration of insulin in blood, and the selectivity against interferants in blood. This review summarizes current insulin detection methods from immunoassays to analytical chemistry, and sensors. We also discuss the challenges and potential of each of the methods towards Point-of-Care insulin detection.

Soluble insulin analogs combining rapid- and long-acting hypoglycemic properties - From an efficient E. coli expression system to a pharmaceutical formulation

The discovery of insulin led to a revolution in diabetes management. Since then, many improvements have been introduced to insulin preparations. The availability of molecular genetic techniques has enabled the creation of insulin analogs by changing the structure of the native protein in order to improve the therapeutic properties. A new expression vector pIBAINS for production of four recombinant human insulin (INS) analogs (GKR, GEKR, AKR, SR) was constructed and overexpressed in the new E. coli 20 strain as a fusion protein with modified human superoxide dismutase (SOD). The SOD gene was used as a signal peptide to enhance the expression of insulin. SOD::INS was manufactured in the form of insoluble inclusion bodies. After cleavage of the fusion protein with trypsin, the released insulin analogs were refolded and purified by reverse-phase high performance liquid chromatography (RP-HPLC). Elongation of chain A, described here for the first time, considerably improved the stability of the selected analogs. Their identity was confirmed with mass spectrometric techniques. The biological activity of the insulin derivatives was tested on rats with experimental diabetes. The obtained results proved that the new analogs described in this paper have the potential to generate prolonged hypoglycemic activity and may allow for even less frequent subcutaneous administration than once-a-day. When applied, all the analogs demonstrate a rapid onset of action. Such a combination renders the proposed biosynthetic insulin unique among already known related formulations.

Effect of insulin analogues on phosphatidyl inositol-3 kinase/Akt signalling in INS-1 rat pancreatic derived β-cells

CONTEXT

Insulin analogues are largely used for the treatment of diabetic patients, but concerns have been raised about their mitogenic/anti-apoptotic potential. It is therefore important to evaluate these analogues in different cell systems.

OBJECTIVE

The aim of this work was to establish the pharmacological profiles of insulin analogues towards PI-3 kinase/Akt pathway in INS-1 β-pancreatic cells.

METHODS

Bioluminescence Resonance Energy Transfer (BRET), in cell western and caspase 3/7 assays, was used to study the effects of ligands.

RESULTS

Among the five analogues evaluated, only glargine stimulated PI-3 kinase/Akt pathway with higher efficiency than insulin, whereas glargine's metabolite M1 was less efficient. However, glargine did not show higher anti-apoptotic efficiency than insulin.

CONCLUSION

Glargine was more efficient than insulin for the activation of PI-3 kinase/Akt pathway, but not for the inhibition of caspase 3/7 activity. Moreover, glargine's metabolite M1 displayed lower efficiency than insulin towards PI-3 kinase/Akt activation and caspase 3/7 inhibition.

Theoretical and computational studies of peptides and receptors of the insulin family

Synergistic interactions among peptides and receptors of the insulin family are required for glucose homeostasis, normal cellular growth and development, proliferation, differentiation and other metabolic processes. The peptides of the insulin family are disulfide-linked single or dual-chain proteins, while receptors are ligand-activated transmembrane glycoproteins of the receptor tyrosine kinase (RTK) superfamily. Binding of ligands to the extracellular domains of receptors is known to initiate signaling via activation of intracellular kinase domains. While the structure of insulin has been known since 1969, recent decades have seen remarkable progress on the structural biology of apo and liganded receptor fragments. Here, we review how this useful structural information (on ligands and receptors) has enabled large-scale atomically-resolved simulations to elucidate the conformational dynamics of these biomolecules. Particularly, applications of molecular dynamics (MD) and Monte Carlo (MC) simulation methods are discussed in various contexts, including studies of isolated ligands, apo-receptors, ligand/receptor complexes and intracellular kinase domains. The review concludes with a brief overview and future outlook for modeling and computational studies in this family of proteins.

Isolation and Characterization of Acetylated Derivative of Recombinant Insulin Lispro Produced in Escherichia coli

Purpose

Insulin lispro is a rapid-acting insulin analogue produced by recombinant DNA technology. As a biosynthetic drug, the protein undergoes strict monitoring aiming for detection and characterization of impurities. The goal of this study was to isolate and identify a derivative of insulin lispro formed during biosynthesis.

Methods

For this purpose, ion exchange chromatography in combination with endoproteinase Glu-C digestion, MALDI-TOF/TOF mass spectrometry and Edman sequencing were employed.

Results

Ion exchange chromatography analysis of related proteins in development batches of recombinant insulin lispro revealed the existence of unknown derivative in excess of the assumed limit. Its molecular mass was 42 Da higher than the theoretical mass of Lys(B31) insulin lispro—one of the expected process-related intermediates. Endoproteinase Glu-C cleavage enabled indication of the modified peptide. Tandem mass spectrometry (MS/MS) allowed to explore the location and type of the modification. The 42 amu shift was present in the mass of y-type ions, while b-type ions were in agreement with theoretical values. It suggested that the modification is present on B31 lysine. Further inquiry revealed the presence of two diagnostic ions for lysine acetylation at m/z 143.1 and 126.1. In addition, the peptide was isolated and sequenced by Edman degradation. Standards of phenylthiohydantoin derivatives of N-ε-acetyl-L-lysine and N-ε-trimethyl-L-lysine, not available commercially, were synthesized in the laboratory. The retention time of the modified residue confirmed its identity as N-ε-acetyl-L-lysine.

Conclusions

The derivative of insulin lispro formed during biosynthesis of the drug was identified to be N-ε-acetyl-L-lysine (B31) insulin lispro.

Diabetes Mellitus, Cognitive Impairment, and Traditional Chinese Medicine

Diabetes mellitus (DM) is a metabolic disorder affecting a large number of people worldwide. Numerous studies have demonstrated that DM can cause damage to multiple systems, leading to complications such as heart disease, cancer, and cerebrovascular disorders. Numerous epidemiological studies have shown that DM is closely associated with dementia and cognition dysfunction, with recent research focusing on the role of DM-mediated cerebrovascular damage in dementia. Despite the therapeutic benefits of antidiabetic agents for the treatment of DM-mediated cognitive dysfunction, most of these pharmaceutical agents are associated with various undesirable side-effects and their long-term benefits are therefore in doubt. Early evidence exists to support the use of traditional Chinese medicine (TCM) interventions, which tend to have minimal toxicity and side-effects. More importantly, these TCM interventions appear to offer significant effects in reducing DM-related complications beyond blood glucose control. However, more research is needed to further validate these claims and to explore their relevant mechanisms of action. The aims of this paper are (1) to provide an updated overview on the association between DM and cognitive dysfunction and (2) to review the scientific evidence underpinning the use of TCM interventions for the treatment and prevention of DM-induced cognitive dysfunction and dementia.

Identifying and meeting the challenges of insulin therapy in type 2 diabetes

Type 2 diabetes mellitus (T2DM) is a chronic illness that requires clinical recognition and treatment of the dual pathophysiologic entities of altered glycemic control and insulin resistance to reduce the risk of long-term micro- and macrovascular complications. Although insulin is one of the most effective and widely used therapeutic options in the management of diabetes, it is used by less than one-half of patients for whom it is recommended. Clinician-, patient-, and health care system-related challenges present numerous obstacles to insulin use in T2DM. Clinicians must remain informed about new insulin products, emerging technologies, and treatment options that have the potential to improve adherence to insulin therapy while optimizing glycemic control and mitigating the risks of therapy. Patient-related challenges may be overcome by actively listening to the patient’s fears and concerns regarding insulin therapy and by educating patients about the importance, rationale, and evolving role of insulin in individualized self-treatment regimens. Enlisting the services of Certified Diabetes Educators and office personnel can help in addressing patient-related challenges. Self-management of diabetes requires improved patient awareness regarding the importance of lifestyle modifications, self-monitoring, and/or continuous glucose monitoring, improved methods of insulin delivery (eg, insulin pens), and the enhanced convenience and safety provided by insulin analogs. Health care system-related challenges may be improved through control of the rising cost of insulin therapy while making it available to patients. To increase the success rate of treatment of T2DM, the 2012 position statement from the American Diabetes Association and the European Association for the Study of Diabetes focused on individualized patient care and provided clinicians with general treatment goals, implementation strategies, and tools to evaluate the quality of care.

(Poly)peptide-based therapy for diabetes mellitus: insulins versus incretins

Insulin therapy remains the standard of care for achieving and maintaining adequate glycemic control, especially in hospitalized patients with critical and noncritical illnesses. Insulin therapy is more effective against elevated fasting glycaemia but less in the reduction of postprandial hyperglycaemia. It is associated with a high incidence of hypoglycemia and weight gain. Contrary, GLP-1 mimetic therapy improves postprandial glycaemia without the hypoglycaemia and weight gain associated with aggressive insulin therapy. Moreover, it has the potential to reduce cardiovascular related morbidity. However, its increased immunogenicity and severe gastrointestinal adverse effects present a huge burden on patients. Thus, a right combination of basal insulin which has lowering effect on fasting plasma glucose and GLP-1 mimetic with its lowering effect on postprandial plasma glucose with minimal gastrointestinal adverse effects, seems the right therapy choice from a clinical point of view for some diabetic patients. In this article, we discuss the pros and cons of the use of insulin analogues and GLP-1 mimetics that are associated with the treatment of type 2 diabetes.

A direct comparison of the pharmacodynamic properties of insulin detemir and neutral protamine lispro insulin in patients with type 1 diabetes

AIMS

To compare the pharmacodynamic properties of insulin detemir (detemir) and neutral protamine lispro (NPL) insulin using a euglycaemic glucose clamp.

METHODS

In a double-blind, crossover study, 30 patients with C-peptide negative type 1 diabetes were randomly assigned to a single dose (0.4 U/kg) of detemir and NPL. Plasma glucose (PG) was normalized with a variable insulin infusion and then decreased stepwise, followed by a euglycaemic clamp at 5.5 mmol/l over 32 h. Duration of action was defined as time from dosing until PG exceeded 8.3 mmol/l for at least 30 min.

RESULTS

Duration of action was similar for detemir [23.0 (range 2.25-32) h] and NPL [22.0 (9.5-32) h], p = 0.55. Using glucose infusion rate (GIR) parameters, detemir showed a flatter pharmacodynamic profile versus NPL: area under the curve, AUC(GIR) ((0-32))  = 1326 vs. 1841 mg/kg, p < 0.01 (detemir vs. NPL, respectively); AUC(GIR) ((0-12))  = 784 vs. 1392 mg/kg, p < 0.05; AUC(GIR) ((12-32))  = 455 vs. 274 mg/kg, p = 0.051; GIR(late) (12-32)/GIR(early) (0-12) ratio = 0.33 vs. 0.04, p < 0.001. Detemir also showed a lower and later peak of action than NPL [GIR(max) 2.0 vs. 3.2 mg/kg/min, p < 0.01; T(max) 9.1 (95% confidence interval: 3.0-14.7) vs. 7.0 h (1.8-15.2)].

CONCLUSIONS

Detemir and NPL had similar duration of action of approximately 24 h in patients with type 1 diabetes. Compared with NPL, detemir had a flatter profile with a more even distribution of metabolic effect over 24 h.

Blood serum antibody analysis and long-term follow-up of patients treated with recombinant human bone morphogenetic protein-2 in the lumbar spine

STUDY DESIGN

Prospective, longitudinal cohort study.

OBJECTIVE

To examine the incidence of bone morphogenetic protein (BMP)-2 antibody formation in lumbar spine applications and to determine the clinical significance of an antibody response.

SUMMARY OF BACKGROUND DATA

Immune responses can affect the safety and efficacy profile of recombinant proteins. Type, incidence, and time course of antibody formation were evaluated in clinical studies investigating recombinant human bone morphogenetic protein (rhBMP)-2 in spinal arthrodesis.

METHODS

Analysis of antibody formation to BMP-2, bovine collagen, and human collagen was performed after three prospective clinical studies investigating rhBMP-2 in single-level lumbar spinal arthrodesis. Two studies investigated rhBMP-2 applied to an absorbable collagen sponge at 1.5 mg/cm3 in lumbar interbody fusion (n=449); one study investigated rhBMP-2 applied to a ceramic and collagen compression-resistant matrix at 2.0 mg/cm3 in instrumented posterolateral fusion (n=239). Control patients received iliac crest bone graft (n=360). Two validated enzyme-linked immunosorbent assays were used to test for BMP-2 antibodies. Neutralizing antibodies were assessed using a cell bioassay. The incidence of antibodies to bovine and human collagen was determined. Radiographic and clinical outcome data were assessed to determine whether antibodies were correlated to patient outcomes.

RESULTS

BMP-2 antibody rates ranged from 0.8% to 6.4% in rhBMP-2 patients and from 0% to 2.3% in control patients. Formation of BMP-2 antibodies peaked within the first 3 months and returned toward baseline values by 12 months. No neutralizing antibodies were detected. Bovine collagen antibody rates ranged from 12.7% to 18.8% in the rhBMP-2 patients and from 12.9% to 21.2% in the control patients. No antibodies to human collagen were detected. Adverse event rates were similar in antibody-positive and antibody-negative patients. BMP-2 antibodies did not affect bridging bone rates.

CONCLUSION

Formation of anti-BMP-2 antibodies was low and transient. No neutralizing antibodies were observed. Formation of antibodies did not affect fusion success or appear to have clinical sequelae.

pH- and sugar-sensitive layer-by-layer films and microcapsules for drug delivery

The present review provides an overview on the recent progress in the development of pH- and sugar-sensitive layer-by-layer (LbL) thin films and microcapsules in relation to their potential applications in drug delivery. pH-sensitive LbL films and microcapsules have been studied for the development of peptide and protein drug delivery systems to the gastrointestinal tract, anti-cancer drugs to tumor cells, anti-inflammatory drugs to inflamed tissues, and the intracellular delivery of DNA, where pH is shifted from neutral to acidic. pH-induced decomposition or permeability changes of LbL films and microcapsules form the basis for the pH-sensitive release of drugs. Sugar-sensitive LbL films and microcapsules have been studied mainly for the development of an artificial pancreas that can release insulin in response to the presence of glucose. Therefore, glucose oxidase, lectin, and phenylboronic acid have been used for the construction of glucose-sensitive LbL films and microcapsules. LbL film-coated islet cells are also candidates for an artificial pancreas. An artificial pancreas would make a significant contribution to improving the quality of life of diabetic patients by replacing repeated subcutaneous insulin injections.

Insights in regulated bioanalysis of human insulin and insulin analogs by immunoanalytical methods

Despite the long and illustrious history of insulin and insulin analogs as important biotherapeutics, the regulated bioanalysis (in this article, regulated bioanalysis refers to the formalized process for generating bioanalytical data to support pharmacokinetic and toxicokinetic assessments intended for development of insulin and insulin analogs as biotherapeutics, as opposed to the analytical process used for measuring insulin as a biomarker) of these peptides remains a challenging endeavor for a number of reasons. Paramount is the fact that the therapeutic concentrations are often low in serum/plasma and not too dissimilar from the endogenous level, particularly in patients with insulin resistance, such as Type 2 diabetes mellitus. Accordingly, this perspective was written to provide helpful background information for the design and conduct of immunoassays to support regulated bioanalysis of insulin and insulin analogs. Specifically, it highlights the technical challenges for determination of insulin and insulin analogs by immunoanalytical methods that are intended to support evaluations of pharmacokinetics and toxicokinetics. In a broader sense, this perspective describes the general bioanalytical issues that are common to regulated bioanalysis of peptides and articulates some of the bioanalytical differences between conventional monoclonal antibodies and peptide therapeutics.

A review of modern insulin analogue pharmacokinetic and pharmacodynamic profiles in type 2 diabetes: improvements and limitations

Insulin analogues have been engineered to enhance desired molecular properties without altering immunogenicity. The majority of insulin pharmacology studies are conducted in healthy volunteers and patients with type 1 diabetes. At present, there are more patients with type 2 than type 1 diabetes receiving insulin treatment. As the responsibility for initiating insulin therapy in these patients continues to shift to primary care, it will be important for general practitioners to understand the different pharmacological properties of insulin preparations in patients with type 2 diabetes, so that treatment can be adapted to meet patients' physiological and lifestyle requirements. The purpose of this review is to summarize pharmacological studies of insulin analogues in patients with type 2 diabetes. Faster onset of action of rapid acting insulin analogues has improved postprandial glycaemic control. Biphasic insulin analogues are associated with a lower incidence of nocturnal hypoglycaemia compared with human biphasic preparations and allow for intensification from once to twice or thrice daily dosing. More predictable glycaemic-lowering profiles of the insulin analogues have also led to reductions in nocturnal hypoglycaemia, particularly comparing long-acting insulin analogues with protaminated human insulin. Enhancing insulin self-association and reversible binding with albumin has led to further reductions in variability. However, improvements can still be made. Effective once daily clinical dosing of long-acting insulin analogues is not possible in all patients. In addition, the protaminated component of biphasic insulin analogues do not provide the duration of action or profile for physiological basal insulin replacement and neither insulin glargine nor insulin detemir are suitable for mixing with other insulin analogues as this would substantially alter their pharmacokinetic properties. Enhancing the pharmacological predictability and extending the duration of action could simplify insulin titration and further reduce the incidence of hypoglycaemia.

Symptoms of infectious diseases in travelers with diabetes mellitus: a prospective study with matched controls

BACKGROUND

Travelers with diabetes mellitus to developing countries are thought to have symptomatic infectious diseases more often and longer than travelers without diabetes. Evidence for this is needed. This study evaluates whether travelers with diabetes are at increased risk of symptomatic infectious diseases.

METHODS

A prospective study was performed between October 2003 and February 2008 among adult medication-dependent travelers with diabetes, with their healthy travel companions without diabetes serving as matched controls. Thus, travelers with diabetes and controls were assumed to have comparable exposure to infection. Data on symptoms of infectious diseases were recorded by using a structured diary.

RESULTS

Among 70 travelers with insulin-dependent diabetes, the incidence of travel-related diarrhea was 0.99 per person-month, and the median number of symptomatic days 1.54 per month. For their 70 controls, figures were 0.74 and 1.57, respectively (p > 0.05). Among 82 travelers with non-insulin-dependent diabetes, incidence was 0.75, and the median number of symptomatic days was 1.68. For their 82 controls, figures were 0.70 and 1.68, respectively (p > 0.05). As for other symptoms, no significant travel-related differences were found. Only 17% of travelers with diabetes suffering from diarrhea used their stand-by antibiotics.

CONCLUSIONS

Medication-dependent travelers with diabetes traveling to developing countries do not have symptomatic infectious diseases more often or longer than travelers without diabetes. Routine prescription of stand-by antibiotics for travelers with diabetes to areas with good health facilities is probably not more useful than for healthy travelers.

Are analogue insulins superior to human insulin in clinical practice?

Insulin analogues were designed to provide more physiologic pharmacokinetic and pharmacodynamic properties compared with human insulin. This article examines the literature over a 2-year period, focusing on studies directly comparing analogue and human insulin in controlled clinical trials and large observational studies documenting the introduction of, or change to, analogue insulin in clinical practice. Findings indicate that analogues provide objective benefits that include improved glycemic control, lower risk of hypoglycemia, lower glucose variability, and (for insulin detemir) reduced weight gain. Recent data with analogues also explore their safety and efficacy in special patient groups such as children and adolescents. These data complement increasing evidence that analogues offer improved acceptability and accessibility to people with diabetes.

Impact of Absorption and Transport on Intelligent Therapeutics and Nano-scale Delivery of Protein Therapeutic Agents

The combination of materials design and advances in nanotechnology has led to the development of new therapeutic protein delivery systems. The pulmonary, nasal, buccal and other routes have been investigated as delivery options for protein therapy, but none result in improved patient compliances and patient quality of life as the oral route. For the oral administration of these new systems, an understanding of protein transport is essential because of the dynamic nature of the gastrointestinal tract and the barriers to transport that exist.Models have been developed to describe the transport between the gastrointestinal lumen and the bloodstream, and laboratory techniques like cell culture provide a means to investigate the absorption and transport of many therapeutic agents. Biomaterials, including stimuli-sensitive complexation hydrogels, have been investigated as promising carriers for oral delivery. However, the need to develop models that accurately predict protein blood concentration as a function of the material structure and properties still exists.

Dual behavior of sodium dodecyl sulfate as enhancer or suppressor of insulin aggregation and chaperone-like activity of camel alphaS(1)-casein

Sodium dodecyl sulfate (SDS) at low concentrations considerably enhanced insulin aggregation and reduced the chaperone-like activity of purified camel alphaS(1)-casein (alphaS(1)-CN). These observed changes were the result of repulsive electrostatic interactions between both negative charged head groups of SDS and alphaS(1)-CN, and the net negative charge of insulin molecules, resulting in the greater exposure of hydrophobic patches of insulin and its enhanced aggregation. In contrast, enhanced hydrophobic interactions were primarily responsible for the conformational changes observed in insulin and alphaS(1)-CN at high SDS concentrations, resulting in increased binding of SDS and alphaS(1)-CN to insulin and its reduced aggregation.

Novel iron-polysaccharide multilayered microcapsules for controlled insulin release

Iron-polysaccharide complexes have been extensively used for the treatment of iron-deficiency anemia without side-effects. In this study, insulin-loaded microcapsules were prepared via layer-by-layer deposition of oppositely charged Fe(3+) and dextran sulfate (DS) onto the surface of insulin microparticles. Fe(3+) was combined with DS via both electrostatic interaction and chemical complexation process, leading to the formation of a stable complex of Fe(3+)/DS. Subsequently, protamine was used as the outermost layer of the insulin-loaded microcapsules to facilitate nuclear delivery. The sufficient charge reversal with successive deposition cycles and successful fabrication of hollow microcapsules provided strong evidence for the growth of (Fe(3+)/DS)(n) multilayer on the surface of microparticles. The experiments showed that the microcapsules successfully entrapped insulin with encapsulation efficiency of 70.56+/-0.97% and drug loading content of 46.15+/-0.97%. It was found that the release time and hypoglycemic effect increased as the number of deposited bilayers increased. The insulin-loaded microcapsules significantly improved glucose tolerance from 2 h (free insulin) to even 12 h (insulin-loaded microcapsules with 10 bilayers). Moreover, the microcapsules with protamine as the outermost layer displayed a prolonged and stable glucose-lowering profile over a period of over 6 h compared with Fe(3+) as the outermost layer. These findings indicate that such microcapsules can be a promising approach for the construction of an effective controlled release delivery system of insulin as well as other proteins with short half-life time.

Insulin glulisine: an evaluation of its pharmacodynamic properties and clinical application

OBJECTIVE

To evaluate the pharmacodynamic properties, efficacy, safety, and clinical application of insulin glulisine, a rapid-acting insulin analog, in the treatment of diabetes mellitus in ambulatory and hospitalized patients.

DATA SOURCES

Searches were performed with the headings glulisine, insulin analog, [LysB3, GluB29] insulin, insulin glulisine, rDNA insulin, rapid-acting insulin, SoloStar, safety, efficacy, pharmacodynamics, and cost analysis within MEDLINE and PubMed, American Diabetes Association (ADA), the Food and Drug Administration (FDA), and Sanofi-aventis Pharmaceuticals (1990-August 2008).

STUDY SELECTION AND DATA EXTRACTION

Phase 1, Phase 2, Phase 3, and postmarketing trials examining the efficacy and safety of glulisine in type 1 or type 2 diabetes were reviewed. Studies published as abstracts and the manufacturer's product information supplemented data absent from clinical trials.

DATA SYNTHESIS

Insulin glulisine is a rapid-acting insulin with relative equivalence in efficacy and safety to other short- and rapid-acting insulins. Glulisine's onset of action of 20 minutes and 4-hour duration of action allow for bolus administration 15-20 minutes prior to or up to 20 minutes after meals. Clinical trials have demonstrated the safety and efficacy in adults with type 1 or type 2 diabetes. Several studies indicated a statistically significant decrease of hemoglobin A1C (A1C) with glulisine compared with regular insulin (0.10 decrease); however, no difference in A1C control was found compared with insulin aspart or lispro. Significant adverse effects appear to be limited to localized and systemic allergic reactions and hypoglycemia.

CONCLUSIONS

Insulin glulisine is a safe and effective rapid-acting insulin analog for the treatment of adults with diabetes. Clinical benefit over other short- and rapid-acting insulin products is not established. Addition of insulin glulisine to a formulary should be based on institution-specific availability and cost differences between glulisine, lispro, and aspart in the absence of superiority of clinical efficacy or safety and data beyond 26 weeks.

Tolerability, safety and adherence to treatment with insulin detemir injection in the treatment of type 2 diabetes

The progressive nature of type 2 diabetes poses challenges in the clinic: treatment must be continually reviewed and adjusted in response to the patient's changing pathophysiology. Ultimately, insulin replacement therapy will be necessary as the physiological insulin response is compromised. The modern basal insulin analog insulin detemir has been the subject of several clinical trials and observational studies in type 2 diabetes. Compared with NPH insulin, insulin detemir offers an improved balance between achieving current glycemic targets with acceptable tolerability. Insulin detemir also has a unique weight-sparing effect which is associated with body mass index, and this may be a particular advantage to obese patients with type 2 diabetes. This review summarizes data from key clinical studies of insulin detemir, and also provides insights from observational studies.