Insulin analogs with improved pharmacokinetic profiles

Preliminary application of a new bolus insulin model for type 1 diabetes

BACKGROUND

Previous work derived a theoretically rigorous bolus insulin model. It was shown that the new model predicts insulin response of subjects without diabetes substantially better than the carbohydrate counting method (CHOcm). As most individuals with type 1 diabetes use the CHOcm, this article investigates if the new model can be applied to them.

METHODS

Equations are derived to characterize a person with type 1 diabetes. These are implemented on a cell phone that calculates bolus insulin dosages. In a small feasibility study the cell phone was used by 11 patients. Basal insulin remained unchanged. The subjects were experienced in the CHOcm and were using it at the start of the study. Continuous glucose monitoring data were recorded to capture blood glucose (BG) control elements such as average BG and tightness of control, as well as hypoglycemic and hyperglycemic events. A new rating method was proposed to estimate BG control. It (or a derivative thereof ) may in the future become a valuable measure of total glycemic control. We used the status quo ante versus status quo approach to find indicative results. BG control for the same group when using CHOcm (status quo ante) was compared with BG control when using the new application (status quo).

RESULTS

Patients found the new application on the cell phone practical. Indicative results also showed BG control improvements, although the subjects were more experienced in the CHOcm. Depending on the weights assigned to the underlying control elements an improvement of between 26% and 64% was found.

CONCLUSION

An indicative study (status quo ante vs. status quo) on 11 patients with type 1 diabetes showed that the new method can be practically and successfully applied on a cell phone. Glycemic control even improved. A new BG rating method was proposed. We believe there is enough preliminary indication to warrant a more detailed clinical trial in future by an institution with adequate funds and access to more patients.

Diabetes mellitus and increased risk of cancer: focus on metformin and the insulin analogs

Type 2 diabetes mellitus has been associated with an increased risk of hepatic, pancreatic, colon, endometrial, breast, and bladder cancer. Although a mechanism of action for the increased risk has been postulated, no definitive evidence has been completely elucidated in the medical literature. Results of recently released studies documented the use of specific antidiabetic drugs with increased rates of cancer. The insulin analog glargine was the focus of four observational studies published in 2009 that outlined an increase in the rates of cancer associated with its use. In contrast, the use of metformin has been shown to possibly decrease the rate of specific cancers when used in the treatment of type 2 diabetes. These data regarding cancer risk and antidiabetic drugs are contradictory and at this time are inconclusive. Until results of long-term randomized prospective studies are available to elucidate a correlation with cancer and insulin, we must continue treating diabetes in order to avert the long-term complications of the disease.

Intranasal insulin as a therapeutic option in the treatment of cognitive impairments

The brain is a major target of circulating insulin. Enhancing central nervous insulin action has been shown to improve memory functions in animals as well as in humans, benefitting in particular hippocampus-dependent (declarative) memory. As Alzheimer's disease (AD) is associated with reduced central nervous insulin signaling and attenuated permeation of blood-borne insulin across the blood-brain-barrier, the cognitive decline in AD patients may at least in part be derived from impaired brain insulin signaling. Thus, therapeutic strategies to overcome central nervous system insulin deficiency and resistance might be an attractive option in the treatment of cognitive impairments like AD. Insulin can be effectively delivered directly to the brain via the intranasal route that enables the hormone to bypass the blood-brain barrier and modulate central nervous functions. This review summarizes a series of studies demonstrating beneficial effects of intranasal insulin on memory functions both in healthy humans and in patients with cognitive impairments such as AD. These experiments in humans consistently indicate that enhancing brain insulin signaling by intranasal administration of the hormone improves hippocampus-dependent memory in the absence of adverse side effects. Considering that insulin also acts as a neuroprotective signal, up-regulating brain insulin levels by intranasal insulin administration appears to be a promising approach in the treatment and prevention of central nervous system insulin deficiency and resistance as found in AD.

In vitro metabolic and mitogenic signaling of insulin glargine and its metabolites

Background

Insulin glargine (Lantus®) is a long-acting basal insulin analog that demonstrates effective day-long glycemic control and a lower incidence of hypoglycemia than NPH insulin. After subcutaneous injection insulin glargine is partly converted into the two main metabolites M1 ([Gly^A21]insulin) and M2 ([Gly^A21,des-Thr^B30]insulin). The aim of this study was to characterize the glargine metabolites in vitro with regard to their insulin receptor (IR) and IGF-1 receptor (IGF1R) binding and signaling properties as well as their metabolic and mitogenic activities.

Methods

The affinity of human insulin, insulin glargine and its metabolites to the IR isoforms A and B or IGF1R was analyzed in a competitive binding assay using SPA technology. Receptor autophosphorylation activities were studied via In-Cell Western in CHO and MEF cells overexpressing human IR-A and IR-B or IGF1R, respectively. The metabolic response of the insulins was studied as stimulation of lipid synthesis using primary rat adipocytes. Thymidine incorporation in Saos-2 cells was used to characterize the mitogenic activity.

Conclusions

The binding of insulin glargine and its metabolites M1 and M2 to the IR were similar and correlated well with their corresponding autophosphorylation and metabolic activities in vitro. No differences were found towards the two IR isoforms A or B. Insulin glargine showed a higher affinity for IGF1R than insulin, resulting in a lower EC₅₀ value for autophosphorylation of the receptor and a more potent stimulation of thymidine incorporation in Saos-2 cells. In contrast, the metabolites M1 and M2 were significantly less active in binding to and activation of the IGF1R and their mitogenicity in Saos-2 cells was equal to human insulin. These findings strongly support the idea that insulin glargine metabolites contribute with the same potency as insulin glargine to blood glucose control but lead to significantly reduced growth-promoting activity.

Mid- and high-ratio premix insulin analogues: potential treatment options for patients with type 2 diabetes in need of greater postprandial blood glucose control

Some patients with type 2 diabetes continue to have high postprandial blood glucose levels on twice-daily regimens of 'low-ratio' premix insulin formulations (up to 30% rapid-acting, with 70% protracted insulin). These patients require intensified insulin therapy, which can be provided by a twice- or thrice-daily regimen of mid-ratio (50% rapid-acting and 50% protaminated intermediate-acting insulin - human or analogue) or high-ratio (70% rapid-acting and 30% protaminated insulin - analogue only) premix insulin. Alternatively, a third daily injection of low-ratio premix insulin can be added to the regimen, with the option of incorporating one or more injections of mid- or high-ratio premix as required, and as an alternative to basal-bolus therapy. How these mid- and high-ratio formulations differ from the low-ratio premix insulins is reviewed here, with the aim of identifying the role of these formulations in diabetes management. Glucose clamp studies have shown that premix analogues give serum insulin levels proportional to their percentage of rapid-acting uncomplexed insulin: the higher the proportion, the greater the maximum level reached. Other pharmacokinetic parameters were not always significantly different between the mid- and high-ratio formulations. In clinical trials, postprandial plasma glucose and glycated haemoglobin A1c (HbA(1c)) levels were significantly reduced with thrice-daily mid- /high-ratio premix analogue when compared with twice-daily low-ratio biphasic human insulin (BHI) 30/70 or once-daily insulin glargine. Moreover, glycaemic control with mid-/high-ratio premix analogue was found to be similar to that with a basal-bolus therapy. Mid- and high-ratio premix regimens are generally well tolerated. The frequency of minor hypoglycaemia was reportedly higher with mid- /high-ratio premix analogues than with BHI 30, but nocturnal hypoglycaemia was less frequent. Although there is little evidence that clinical outcomes with mid-ratio premix analogues are different from those with high-ratio, they are useful additions to the low-ratio formulations for the management of diabetes, and addressing postprandial hyperglycaemia in particular.

Design of an insulin analog with enhanced receptor binding selectivity: rationale, structure, and therapeutic implications

Insulin binds with high affinity to the insulin receptor (IR) and with low affinity to the type 1 insulin-like growth factor (IGF) receptor (IGFR). Such cross-binding, which reflects homologies within the insulin-IGF signaling system, is of clinical interest in relation to the association between hyperinsulinemia and colorectal cancer. Here, we employ nonstandard mutagenesis to design an insulin analog with enhanced affinity for the IR but reduced affinity for the IGFR. Unnatural amino acids were introduced by chemical synthesis at the N- and C-capping positions of a recognition alpha-helix (residues A1 and A8). These sites adjoin the hormone-receptor interface as indicated by photocross-linking studies. Specificity is enhanced more than 3-fold on the following: (i) substitution of Gly(A1) by D-Ala or D-Leu, and (ii) substitution of Thr(A8) by diaminobutyric acid (Dab). The crystal structure of [D-Ala(A1),Dab(A8)]insulin, as determined within a T(6) zinc hexamer to a resolution of 1.35 A, is essentially identical to that of human insulin. The nonstandard side chains project into solvent at the edge of a conserved receptor-binding surface shared by insulin and IGF-I. Our results demonstrate that modifications at this edge discriminate between IR and IGFR. Because hyperinsulinemia is typically characterized by a 3-fold increase in integrated postprandial insulin concentrations, we envisage that such insulin analogs may facilitate studies of the initiation and progression of cancer in animal models. Future development of clinical analogs lacking significant IGFR cross-binding may enhance the safety of insulin replacement therapy in patients with type 2 diabetes mellitus at increased risk of colorectal cancer.

Proliferative effect of Apidra (insulin glulisine), a rapid-acting insulin analogue on mammary epithelial cells

The structural modification of insulin results in the generation of insulin analogues that show altered binding affinities to the insulin receptor and/or the IGF-I receptor, and as a consequence insulin analogues may have altered mitogenic potency. We analysed the proliferative effect of the rapid-acting insulin analogue Apidra (insulin glulisine) on mammary epithelial cells. We show that Apidra and Actrapid (recombinant human insulin) have similar proliferative effects on benign MCF10A and tumorigenic MCF7 cells and on epithelial cells of mouse mammary gland. Whereas Apidra and Actrapid induced similar activation of Erk1/2, activation of Akt/PKB by Apidra was significantly weaker compared to regular insulin. As AKT/PKB, an effector of the phosphoinositide 3-kinase pathway, mediates metabolic effects of insulin, we studied induction of hexokinase-2 in MCF7 cells and hexokinase-2 and hexokinase-4 in HepG2 cells by Actrapid and Apidra. Both genes were not significantly induced by Actrapid and Apidra in these cell lines.

Biphasic insulin aspart 30/70 (BIAsp 30) in the treatment of type 1 and type 2 diabetes

The pharmacological advantages of the rapid-acting analog, insulin aspart, over human insulin have contributed to the widespread prescription of the premix, biphasic insulin aspart 30/70 (BIAsp 30), in type 1 (T1DM) and type 2 diabetes (T2DM). This article reviews the available literature on the pharmacology, efficacy and safety of BIAsp 30 in T1DM and T2DM from an online search of the PubMed database. Following injection, BIAsp 30 reaches higher plasma insulin levels more quickly than human premix or basal insulin, giving effective reduction of postprandial hyperglycemia. In T1DM patients, randomized controlled trials (RCTs) have shown that HbA(1c) reduction is similar, but postprandial glycemic control is better, with BIAsp 30 than with human insulin regimens. In T2DM patients, lowering of HbA(1c) and postprandial hyperglycemia with BIAsp 30 compare favorably with optimized oral antidiabetes drug treatment, insulin glargine, and, in obese patients, human premix. An increase in minor hypoglycemia with BIAsp 30 relative to basal insulin has been reported in T2DM patients, but major and nocturnal hypoglycemia rates are generally low. Findings from RCTs in T2DM patients are supported by large observational studies. In summary, BIAsp 30 once to three times daily represents a simple and effective tool for the modern management of diabetes.

Differential lipid profile and hormonal response in type 2 diabetes by exogenous insulin aspart versus the insulin secretagogue repaglinide, at the same glycemic control

Our aim was to study, at the same glycemic control, how treatment with either the insulin secretagogue repaglinide or exogenous insulin aspart affects endogenous insulin secretion, plasma insulin and IAPP (islet amyloid polypeptide) levels, GH-IGF (growth hormone-insulin-like growth factor) axis and plasma lipoprotein concentrations in patients with type 2 diabetes. Five patients, age 65.0+/-4.1 years (mean+/-SE), body weight 82.5+/-5.0 kg, BMI (body mass index) 27.7+/-1.5 kg/m(2) were treated for 10 weeks with repaglinide or insulin aspart in a randomized, cross-over study. At the end of each treatment a 24-h metabolic profile was performed. Blood glucose, C-peptide, free human insulin, free total (human and analogue) insulin, proinsulin, IAPP, IGF-I, IGFBP-1 (IGF binding protein-1), GHBP (growth hormone binding protein) and plasma lipoprotein concentrations were measured. Similar 24-h blood glucose profiles were obtained with repaglinide and insulin aspart treatment. During the repaglinide treatment, the meal related peaks of C-peptide and free human insulin were about twofold higher than during treatment with insulin aspart. Proinsulin, GHBP were higher and IAPP levels tended to be higher during repaglinide compared to insulin aspart. Postprandial plasma total cholesterol, triglycerides and apolipoprotein B concentrations were higher on repaglinide than on insulin aspart treatment. Our results show that, at the same glycemic control, treatment with exogenous insulin aspart in comparison with the insulin secretagogue repaglinide result in a lower endogenous insulin secretion, and a tendency towards a less atherogenic postprandial lipid profile.

Insulin analogues: an example of applied medical science

Insulin analogues were developed to try and achieve more physiological insulin replacement from injection in the subcutaneous site. Their pharmacokinetics and pharmacodynamics differ from human insulin when injected subcutaneously because of alterations in the amino acid sequence of the insulin molecule. The rapid-acting insulin analogues, lispro, aspart and glulisine, have a rapid onset of action and shorter duration of action because of changes to the B26-30 portion of insulin inhibiting formation of dimers and hexamers. They appear to improve postprandial glucose, incidence of hypoglycaemia and patient satisfaction and, when used in combination with basal insulin analogues, improve glycosylated haemoglobin in comparison to conventional insulin therapy. Additionally, they have been successfully used in children, pregnant women, in pump therapy and as part of premixed biphasic regimens. The two basal insulin analogues, glargine and detemir, developed by adjusting the isoelectric point and adding a fatty acid residue, respectively, have a protracted duration of action and a relatively smooth profile. Their pharmacokinetic and pharmacodynamic profiles have been assessed using euglycaemic clamp protocols. Both analogues have a longer duration of action, less of a peak of activity and a reduced variability with repeated injection. There is some evidence to suggest that detemir may have a slight hepatoselective effect. Clinical studies have shown a lower relative risk of hypoglycaemia and detemir appears to have a weight-sparing action. Insulin analogues represent a successful example of applied medical science.

The pharmacokinetic and pharmacodynamic properties of different formulations of biphasic insulin aspart: a randomized, glucose clamp, crossover study

BACKGROUND

Type 2 diabetes patients on premixed insulin are commonly prescribed biphasic insulin with low prandial insulin content, such as biphasic insulin aspart (BIAsp) 30, comprising 30% insulin aspart (IAsp). The new formulations BIAsp 50 and BIAsp 70 contain 50% and 70% soluble IAsp, respectively. We compared the pharmacodynamics (PD) and pharmacokinetics (PK) of BIAsp 30, 50, and 70 and IAsp in a glucose clamp trial.

METHODS

In this randomized, double-blind, crossover study at a clinical research institute, 32 type 1 diabetes patients on basal-bolus therapy each underwent four glucose clamps (clamp level 5 mmol/L, duration 28 h post-dosing [12 h for IAsp]) and received a single dose of 0.4 U/kg BIAsp 30, 50, or 70 and IAsp. Main PD/PK outcome parameters measured were early- and late-phase glucose disposal (area under the curve of glucose infusion rate [AUC(GIR)]), nonesterified fatty acid concentrations, and IAsp concentrations.

RESULTS

With increasing proportions of soluble IAsp, the insulin formulations showed significantly higher early metabolic activity (ratio of AUC(GIR) 0-6 h: BIAsp 50/BIAsp 30 = 1.28 [P < 0.001], BIAsp 70/BIAsp 50 = 1.18 [P < 0.001), IAsp/BIAsp 70 = 1.15 [P < 0.01]) and lower late metabolic activity (ratio of AUC(GIR) 12-28 h: BIAsp 50/BIAsp 30 = 0.17 [P < 0.01], BIAsp 70/BIAsp 50 = 0.21 [P < 0.05]). Likewise, early IAsp levels were significantly greater and late PK concentrations were significantly lower with increasing proportion of soluble IAsp.

CONCLUSIONS

There are significant differences between the early and late PD and PK effects among BIAsp 30, 50, and 70 and IAsp that should allow tailored treatment with the convenience of prandial and basal insulin in each injection.

Diabetes mellitus modeling and short-term prediction based on blood glucose measurements

Insulin-Dependent Diabetes Mellitus (IDDM) is a chronic disease characterized by the inability of the pancreas to produce sufficient amounts of insulin. Daily compensation of the deficiency requires 4-6 insulin injections to be taken daily, the aim of this insulin therapy being to maintain normoglycemia - i.e., a blood glucose level between 4 and 7mmol/l. To determine the quantity and timing of these injections, various different approaches are used. Currently, mostly qualitative and semi-quantitative models and reasoning are used to design such a therapy. Here, an attempt is made to show how system identification and control may be used to estimate predictive quantitative models to be used in design of optimal insulin regimens. The system was divided into three subsystems, the insulin subsystem, the glucose subsystem and the insulin-glucose interaction. The insulin subsystem aims to describe the absorption of injected insulin from the subcutaneous depots and the glucose subsystem the absorption of glucose from the gut following a meal. These subsystems were modeled using compartment models and proposed models found in the literature. Several black-box models and grey-box models describing the insulin/glucose interaction were developed and analyzed. These models were fitted to real data monitored by an IDDM patient. Many difficulties were encountered, typical of biomedical systems: Non-uniform and scarce sampling, time-varying dynamics and severe nonlinearities were some of the difficulties encountered during the modeling. None of the proposed models were able to describe the system accurately in all aspects during all conditions. However, all the linear models shared some dynamics. Based on the estimated models, short-term blood glucose predictors for up to two-hour-ahead blood glucose prediction were designed. Furthermore, we explored the issues that arise when applying prediction theory and control to short-term blood glucose prediction.

A subcutaneous insulin pharmacokinetic model for computer simulation in a diabetes decision support role: model structure and parameter identification

OBJECTIVE

The goal of this study was to develop a unified physiological subcutaneous (SC) insulin absorption model for computer simulation in a clinical diabetes decision support role. The model must model the plasma insulin appearance of a wide range of current insulins, especially monomer insulin and insulin glargine, utilizing common chemical states and transport rates, where appropriate.

METHODS

A compartmental model was developed with 13 patient-specific model parameters covering six diverse insulin types [rapid-acting, regular, neutral protamine Hagedorn (NPH), lente, ultralente, and glargine insulin]. Model parameters were identified using 37 sets of mean plasma insulin time-course data from an extensive literature review via nonlinear optimization methods.

RESULTS

All fitted parameters have a coefficient of variation <100% (median 51.3%, 95th percentile 3.6-60.6%) and can be considered a posteriori identifiable.

CONCLUSION

A model is presented to describe SC injected insulin appearance in plasma in a diabetes decision support role. Clinically current insulin types (monomeric insulin, regular insulin, NPH, insulin, and glargine) and older insulin types (lente and ultralente) are included in a unified framework that accounts for nonlinear concentration and dose dependency. Future work requires clinical validation using published pharmacokinetic studies.

Getting closer to physiologic insulin secretion

BACKGROUND

The goal of insulin replacement therapy in diabetes mellitus (DM) is to recreate a normal physiologic insulin supply throughout the day.

OBJECTIVE

This article reviewed the use of rapid acting insulin analogues in recreating physiologic postprandial insulin responses.

METHODS

This review article was based on a presentation at a satellite symposium entitled "Realising the Value of Modern Insulins: Reaching Further with Rapid-Acting Insulin Analogues" that was convened during the XIXth World Diabetes Congress, December 3, 2006, in Cape Town, South Africa.

RESULTS

In the context of mealtime insulin supply, recreating physiologic postprandial insulin responses requires rapid availability of insulin within a short time of eating and a duration of action that does not extend into the late postprandial period. Conventional human insulin is not ideally suited to SC injection, with its slow onset of action and dose-dependent duration of action. The rapid-acting insulin analogues have been designed to address these deficiencies, with more rapid onset of action, higher maximal effects, and consequently better postprandial glycemic control. These properties have been reported in patients with type 1 and type 2 DM, as well as in nondiabetic individuals in euglycemic clamp studies. Rapid-acting insulin analogues are also of particular interest in people with diabetic nephropathy, women with gestational DM, and elderly patients with DM.

CONCLUSIONS

Compared with soluble human (regular) insulin, rapid-acting insulin analogues have a more rapid onset of action and a shorter duration of action. Their potential in special patient groups is now being established in clinical research and in everyday practice.

Pharmacokinetic and pharmacodynamic advantages of insulin analogues and premixed insulin analogues over human insulins: impact on efficacy and safety

Human insulin preparations administered to patients with diabetes mellitus fail to reproduce the normal physiologic pattern of insulin secretion. Modifications have been made in the amino acid sequence of the insulin molecule with the aim of overcoming the pharmacokinetic shortcomings of human insulins. Such modifications have produced long-acting analogues, with relatively flat time-action profiles, for controlling glycemic levels between meals; and rapid-acting analogues with a fast onset and short duration of action, for controlling postprandial hyperglycemia. Premixed formulations of the rapid-acting analogues, containing both rapid-acting soluble and intermediate-acting protaminated forms, are also available. Trials of long-acting insulin analogues have consistently shown efficacy in controlling fasting plasma glucose and glycosylated hemoglobin (HbA1c), as well as a markedly reduced risk of hypoglycemia compared with neutral protamine Hagedorn insulin. The rapid-acting and premixed analogues offer better control of postprandial glucose excursions than do regular human insulin, resulting in similar or lower HbA1c levels. Furthermore, the analogues can offer patients greater flexibility and more convenience in administration compared with human insulins. This review provides an overview of the insulin analogues available today and describes their structure, pharmacokinetics, pharmacodynamics, efficacy, and safety.

Six-month multicentric, open-label, randomized trial of twice-daily injections of biphasic insulin aspart 30 versus multiple daily injections of insulin aspart in Japanese type 2 diabetic patients (JDDM 11)

To evaluate glycemic control using convenience-oriented biphasic insulin analog compared with intensified insulin therapy, we conducted a 6-month multicentric, open-label, randomized trial in Japanese insulin-naive patients with type 2 diabetes mellitus. A total of 160 adult patients at 19 centers were randomized into two groups: those who received twice-daily injections of biphasic insulin aspart 30 and those on three-times-daily injections of insulin aspart with or without NPH insulin (multiple daily injections). At 6 months, mean HbA(1c) decreased by approximately 2.5% in both groups. Reduction of HbA(1c) on both regimens was better in patients whose prior therapy before starting the study was only diet and exercise (-5.0%) than in patients who were previously taking oral antidiabetic agents (-1.0%). No incidence of major hypoglycemia was observed in either regimen. These results suggest that convenience-oriented insulin therapy using biphasic insulin analog is as useful as intensified insulin therapy with insulin analog for the treatment of type 2 diabetes mellitus over 6 months. Furthermore, early induction of insulin therapy in individuals hitherto using only diet and exercise may provide good glycemic control. This study suggests that convenience-oriented biphasic insulin aspart 30 might be a useful option for the treatment of type 2 diabetes mellitus, especially for insulin-naive patients over 6 months, although it should be changed to another regimen when expected efficacy is not obtained.

Transferring type 2 diabetes patients with uncontrolled glycaemia from biphasic human insulin to biphasic insulin aspart 30: experiences from the PRESENT study

AIM

The Physician's Routine Evaluation of Safety and Efficacy of NovoMix* 30 Therapy (PRESENT) aims to assess the safety and efficacy of biphasic insulin aspart (BIAsp30) used in routine clinical practice.

METHODS

This was a large, multi-national, multi-centre, prospective, 6-month study in type 2 diabetes mellitus patients who were prescribed BIAsp30. Efficacy endpoints included changes in HbA(1c), fasting plasma glucose (FPG), postprandial plasma glucose (PPPG), and proportion who achieved target HbA(1c) < 7%. Changes from baseline were analysed using paired t-test. Safety endpoints were incidence and rate of hypoglycaemic episodes. A subgroup of patients previously uncontrolled (HbA(1c) > or = 7.0%) on biphasic human insulin (BHI) were analysed.

RESULTS

Glycaemia improved significantly (mean +/- SD): HbA(1c) by 1.58 +/- 1.69% points (from 9.32 +/- 1.64% to 7.70 +/- 1.29%), FPG by 2.92 +/- 3.71 mmol/L and PPPG by 4.75 +/- 4.87 mmol/L. The incidence of hypoglycaemic episodes decreased over time, from 38.7% (baseline) to 20.8% (6 months). Episodes were mostly minor (reduced from 37.7 to 20.6% at 6 months), occurring during the day (reduced from 31.5 to 17.1% at 6 months). Major episodes were less frequently reported (reduced from 5.0 to 0.4% at 6 months). The rate of hypoglycaemia (episodes/patient year) from baseline to end of study decreased over time for overall (8.9-2.2), major (0.7-0.1), minor (8.2-2.2) and nocturnal (2.9-0.5) episodes.

CONCLUSIONS

In this observational study, in the type 2 diabetes mellitus patients who were poorly controlled on BHI, glycaemia improved when transferred to BIAsp30, and a lower incidence or rate of hypoglycaemia was observed in these patients.

The role of the lymphatic system in subcutaneous absorption of macromolecules in the rat model

The purpose of this study was to assess the contribution of lymphatics to the systemic bioavailability of macromolecules following SC administration in a rat model. The rat model included continuous lymph collection from the thoracic lymph duct and concurrent serial blood sampling from freely moving animals. A thoracic lymph duct-jugular vein shunt produced by an implanted connective cannula, and maintained during the recovery period, enabled superior rat survival and prevented lymphatic cannula occlusion. The SC absorption of three macromolecules (bovine insulin, bovine serum albumin, and recombinant human erythropoietin alpha) was assessed in comparison to the non-lymph cannulated control group. For all tested molecules, only minimal amounts (less than 3%) of the SC administered dose were detected in the collected lymph. In the rat model, following SC administration, the macromolecules were absorbed mainly through the blood capillaries with minimal contribution of the lymphatic system to systemic bioavailability. The relatively small elevation in the lymphatic concentration, which occurred in all molecules, may be attributed to the redistribution of the molecules from the blood to the interstitial fluid compartment. These findings are important since rodents are commonly used in preclinical evaluation of macromolecular drugs.

Comparison of the pharmacokinetic and pharmacodynamic profiles of biphasic insulin aspart 50 and 30 in patients with type 2 diabetes mellitus: a single-center, randomized, double-blind, two-period, crossover trial in Japan

BACKGROUND

To overcome the complicated mixing procedures required in the use of insulin formulations, premixed formulations consisting of rapid-acting and intermediate-type insulin in various mixing proportions have been developed. Biphasic insulin aspart 50 (BIAsp50) and 30 (BlAsp30) are 2 premixed formulations containing the active ingredient insulin aspart (IAsp) and consisting of a rapid-acting component soluble IAsp) and intermediate-acting component (protamine-crystallized protracted IAsp) in ratios of 50/50 and 30/70, respectively. These formulations are provided with the expectation that BIAsp30 and BIAsp50 will be beneficial for patients needing to improve their postprandial blood glucose control without changing their dietary habits and lifestyles. BIAsp30 has been widely used in medical practice, whereas BIAsp50 is being investigated in clinical trials.

OBJECTIVE

The aim of this study was to compare the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of BIAsp50 (test) and BIAsp30 (reference) after single-dose SC injection in patients with type 2 diabetes mellitus.

METHODS

This single-center, randomized, doubleblind, 2-period, crossover trial was conducted at the H.E.C. Science Clinic, Yokohama, Japan. Male and female patients aged > or = 20 years with a > or = 1 year history of type 2 diabetes were eligible. Patients were randomly assigned to 1 of 2 treatment sequences: group A received BIAsp30 in period 1 and BIAsp50 in period 2; group B received BIAsp50 in period 1 and BIAsp30 in period 2. All treatments were administered as an SC injection of a single dose (0.3 U/kg). The study periods were separated by a washout period of 4 to 21 days. For PK analysis of IAsp (maximum serum IAsp concentration [C(max,IAsp); primary end point], AUC of serum IAsp 0 to 120, 240, and 480 minutes after administration [AUC(0-120 min,IAspl), AUC(0-240 min,IAsp), and AUC(0-480 min,IAsp5) respectively], and time to (Cmax,IAsp) [T(max,IAsp)] ), blood samples were drawn immediately before (baseline) and at prespecified time points over 480 minutes after administration. The PD profiles of BIAsp50 and BIAsp30 were also examined by comparing the time course of the glucose infusion rate (GIR) using the euglycemic clamp technique. The PD end points were AUC of GIR 0 to 120 minutes after administration (AUC(0-120 min,GIR)), maximum GIR (GIR(max)), and time to GIRmax (T(max,GIR)). Tolerability was assessed using physical examination, including vital sign measurement, electrocardiography, body weight, adverse events (AEs), and clinical laboratory analysis (hematology and serum biochemistry).

RESULTS

Six men and 4 women were enrolled in the study (mean age, 62.4 years; mean body weight, 58.3 kg; mean body mass index, 22.22 kg/m(2); mean duration of diabetes, 9.53 years; and mean glycosylated hemoglobin concentration, 6.07%). Mean(Cmax,IAsp) with BIAsp50 was 63% higher than that for BIAsp30 (P < 0.002). The BIAsp50/BIAsp30 ratio with AUC(0-120 min,IAsp) was 1.68 (95% CI, 1.31-2.14). The BIAsp50/BIAsp30 ratiofor AUC(0-120 min,GIR) was 1.31 (95% CI, 1.02-1.68). A total of 9 AEs were reported in 5 patients, but none of the AEs were considered related to the study drug.

CONCLUSION

In this small PK/PD study in adults with type 2 diabetes in Japan, mean C(max,IAsp) was significantly higher with BIAsp50 than with BIAsp30, and AUC(0-120 min,IAsp) and AUC(0-120 min,GIR) were higher with BIAsp50 than with BIAsp30.

Premixed insulin treatment for type 2 diabetes: analogue or human?

The progressive nature of type 2 diabetes makes insulin initiation a necessary therapeutic step for many patients. Premixed insulin formulations containing both basal and prandial insulin (so called biphasic insulin) are often prescribed because they are superior to long- or intermediate-acting insulin in obtaining good metabolic control. In addition, they are considered as an attractive alternative to classical basal-bolus therapy as fewer daily injections are required. Premixed insulin formulations include conventional (e.g. biphasic human insulin 70/30, or 30/70 in European countries, BHI 30) and newer premixed human analogues (e.g. biphasic insulin aspart 70/30, or 30/70 in Europe, BIAsp 30; insulin lispro mix 75/25-Mix 75/25, or Mix 25/75 in Europe). Like conventional premixed human insulin, premixed insulin analogues contain a fixed proportion of soluble, rapid-acting insulin analogue, with protaminated analogue comprising the remainder. Unlike conventional premixes, analogue premixes have more physiological pharmacokinetic and therapeutically more desirable pharmacodynamic profiles than premixed human insulin. Consequently, postprandial glycaemic control is better with premixed insulin analogues than with premixed human insulin. In nontreat-to-target registration trials, the lowering of haemoglobin A(1c) with premixed insulin analogues was not inferior to that seen with premixed human insulin. Minor hypoglycaemia was similar for premixed analogue and premixed human insulins, while major hypoglycaemia appears to be rare with either formulation. The occurrence of adverse events, other than hypoglycaemia, was also similar between various premix insulins. The premixed insulin analogues, BIAsp 30 and Mix 75/25, like the fast-acting analogues from which they are derived, also allow flexible injection timing, relative to meal timing, thus improving adherence, compliance and quality of life compared with premixed human insulin. Overall, the evidence suggests that premixed insulin analogues are cost effective and have useful advantages over premixed human insulin for the treatment of type 2 diabetes.

Insulin: a model system for nanomedicine?

One of the predominant aims of insulin therapy for diabetes is to appropriately mimic physiological insulin secretion levels and their correlation with glucose concentration in healthy individuals. This report outlines current methods and their limitations in glycemic control and their possible relationship to insufficient knowledge about the structure and dynamics of the insulin hormone itself. Based on recent experimental and computational work, a possible approach to less-invasive insulin administration is sketched.

Peptide Drug Delivery Strategies for the Treatment of Diabetes

Drug delivery strategies for diabetes have included a wide range of scientific and engineering approaches, including molecular design, formulation and device design. Molecular engineering has resulted in modified pharmacokinetics, such as rapid-acting or slow-release analogs of insulin. Long-acting insulin formulations are designed to meet the body's basal needs, whereas rapid-acting insulin formulations are designed to cover mealtime glucose spikes. Furthermore, the discovery of new therapeutic biomolecules, which like insulin need to be injected, will drive the need for more flexible and universally applicable delivery systems. Formulation design, such as particle engineering, can be used to modify pharmacokinetic profiles. In general, suspension formulations of insulin commonly demonstrate reduced solubility and result in sustained release. Similarly, depot injections can result in precipitation of insulin at the site of injection, again resulting in lower solubility and sustained release. Particle engineering also has been applied to pulmonary formulations for delivery to the deep lung. The creation of novel drug delivery methods for the treatment of diabetes should remove barriers to insulin therapy and increase patient acceptance and compliance. Eliminating routine injections with needle-free injectors, insulin pumps, inhalation, buccal sprays, intra-nasal delivery, and transdermal patches may offer increasingly attractive alternatives.

The use of Fmoc-Lys(Pac)-OH and penicillin G acylase in the preparation of novel semisynthetic insulin analogs

In this paper, we present the detailed synthetic protocol and characterization of Fmoc-Lys(Pac)-OH, its use for the preparation of octapeptides H-Gly-Phe-Tyr-N-MePhe-Thr-Lys(Pac)-Pro-Thr-OH and H-Gly-Phe-Phe-His-Thr-Pro-Lys(Pac)-Thr-OH by solid-phase synthesis, trypsin-catalyzed condensation of these octapeptides with desoctapeptide(B23-B30)-insulin, and penicillin G acylase catalyzed cleavage of phenylacetyl (Pac) group from Nepsilon-amino group of lysine to give novel insulin analogs [TyrB25, N-MePheB26,LysB28,ProB29]-insulin and [HisB26]-insulin. These new analogs display 4 and 78% binding affinity respectively to insulin receptor in rat adipose membranes.

pI-shifted insulin analogs with extended in vivo time action and favorable receptor selectivity

A long-acting (basal) insulin capable of delivering flat, sustained, reproducible glycemic control with once daily administration represents an improvement in the treatment paradigm for both type 1 and type 2 diabetes. Optimization of insulin pharmacodynamics is achievable through structural modification, but often at the expense of alterations in receptor affinity and selectivity. A series of isoelectric point (pI)-shifted insulin analogs based on the human insulin sequence or the GlyA21 acid stable variant were prepared by semi-synthetic methods. The pI shift was achieved through systematic addition of one or more arginine (Arg) or lysine (Lys) residues at the N terminus of the A chain, the N terminus of the B chain, the C terminus of the B chain, or through a combination of additions at two of the three sites. The analogs were evaluated for their affinity for the insulin and IGF-1 receptors, and aqueous solubility under physiological pH conditions. Notably, the presence of positively charged amino acid residues at the N terminus of the A chain was consistently associated with an enhanced insulin to IGF-1 receptor selectivity profile. Increased IGF-1 receptor affinity that results from Arg addition to the C terminus of the B chain was attenuated by cationic extension at the N terminus of the A chain. Analogs 10, 17, and 18 displayed in vitro receptor selectivity similar to that of native insulin and solubility at physiological pH that suggested the potential for extended time action. Accordingly, the in vivo pharmacokinetic and pharmacodynamic profiles of these analogs were established in a somatostatin-induced diabetic dog model. Analog 18 (A0:Arg, A21:Gly, B31:Arg, B32:Arg human insulin) exhibited a pharmacological profile comparable to that of analog 15 (insulin glargine) but with a 4.5-fold more favorable insulin:IGF-1 receptor selectivity. These results demonstrate that the selective combination of positive charge to the N terminus of the A chain and the C terminus of the B chain generates an insulin with sustained pharmacology and a near-native receptor selectivity profile.

Why and how to use insulin therapy earlier in the management of type 2 diabetes

Most patients with type 2 diabetes are inadequately controlled on their current therapy. Suboptimal glycemic control can have devastating consequences, such as retinopathy, nephropathy, neuropathy, and cardiovascular disease that may ultimately lead to mortality. Most patients eventually need insulin therapy, and initiating insulin earlier in the course of type 2 diabetes may lead to optimal glycemic control and prevent or delay diabetes-related complications. Although insulin therapy is the most effective method of managing hyperglycemia, it is often delayed owing to concerns about the complexity and inconvenience of treatment regimens; fear of injections, hypoglycemia or weight gain; and the time required to learn how to effectively manage insulin therapy. The development of insulin analogs, biphasic insulin analogs, and more convenient insulin delivery systems may make insulin therapy more manageable and help more patients achieve their treatment goals.

Intranasal insulin improves memory in humans: superiority of insulin aspart

There is compelling evidence that intranasal administration of regular human insulin (RH-I) improves memory in humans. Owing to the reduced tendency of its molecules to form hexamers, the rapid-acting insulin analog insulin aspart (ASP-I) is more rapidly absorbed than RH-I after subcutaneous administration. Since after intranasal insulin administration, ASP-I may also be expected to access the brain, we examined whether intranasal ASP-I has stronger beneficial effects on declarative memory than RH-I in humans. Acute (40 IU) and long-term (4 x 40 IU/day over 8 weeks) effects of intranasally administered ASP-I, RH-I, and placebo on declarative memory (word lists) were assessed in 36 healthy men in a between-subject design. Plasma insulin and glucose levels were not affected. After 8 weeks of treatment, however, word list recall was improved compared to placebo in both the ASP-I (p<0.01) and the RH-I groups (p<0.05). ASP-I-treated subjects performed even better than those of the RH-I-treated group (p<0.05). Our results indicate that insulin-induced memory improvement can be enhanced by using ASP-I. This finding may be especially relevant for a potential clinical administration of intranasal insulin in the treatment of memory disorders like Alzheimer's disease.

Kinetics of Insulin Adsorption at the Oil–Water Interface and Diffusion Properties of Adsorbed Layers Monitored Using Fluorescence Correlation Spectroscopy

The adsorption of insulin at an oil-water interface was studied with fluorescence correlation spectroscopy (FCS). FCS is able to measure diffusion properties of insulin at nanomolar concentrations, making it possible to detect the very early steps in the adsorption process. Below 20 nM bulk insulin concentration, the insulin molecules adsorbed to the surface diffuse freely at all times during the experiment (a few hours). At higher concentrations, a surprisingly abrupt transition to a slow diffusion phase is observed. Based on the information about both diffusion times and molecular brightness derived from the FCS experiments, we suggest that the transition represents the formation of a fractal network. FCS may be a valuable tool in pharmaceutical formulation science, because it provides information about concentration buildup and phase changes at interfaces formed in drug delivery systems.

Application of SIMSTEX to oligomerization of insulin analogs and mutants

The propensity of various insulins and their analogs to oligomerize was investigated by mass spectrometric methods including measurement of the relative abundances of oligomers in the gas phase and the kinetics of H/D amide exchange. The kinetics of deuterium uptake show a good fit when the exchanging amides are placed in three kinetic groups: fast, intermediate, and slow. r-Human insulin, of the insulins investigated, has fewer amides that exchange at intermediate rates and more that exchange at slow rates, in accord with its higher extent of association in solution. We adapted PLIMSTEX (protein ligand interactions by mass spectrometry, titration, and H/D exchange) to determine protein/ligand affinities in solution, to determine self-association equilibrium constants for proteins, and to apply them to various insulin analogs. We term this adaptation SIMSTEX (self-association interactions using mass spectrometry, self-titration and H/D exchange); it gives affinity constants that compare well with the literature results. The results from SIMSTEX show that some mutants (e.g., GlnB13) have an increased tendency to self-associate, possibly slowing down their action in vivo. Other mutants (e.g., lispro and AspB9) have lower propensities for self-association, thus providing potentially faster-acting analogs for use in controlling diabetes.

Multiple mealtime administration of biphasic insulin aspart 30 versus traditional basal-bolus human insulin treatment in patients with type 1 diabetes

AIM

The aim of this study was to compare the effect of multiple mealtime injections of biphasic insulin aspart 30 (30% fast-acting insulin aspart in the formulation, BIAsp30) to traditional basal-bolus human insulin regimen (HI) on glycaemic control in patients with type 1 diabetes.

METHODS

Twenty-three patients (eight women and 15 men) aged 44.8 (20.6-62.5) years (median and range) with a diabetes duration of 19.5 (1.6-44.6) years completed the study. All eligible patients were randomly assigned to BIAsp30 thrice daily supplied with bedtime NPH insulin when necessary, or basal-bolus HI for 12 weeks and then switched to the alternative regimen for another 12 weeks. The insulin dose adjustments were made by patients on the basis of advice from a diabetes nurse. At end of each treatment period, the patients attended two profile days, 1 week apart for pharmacodynamic and pharmacokinetic assessments. HbA1C was measured at baseline and at the end of each treatment period. A seven-point self-monitored blood glucose (SMBG) was obtained twice weekly.

RESULTS

In comparison with HI, multiple mealtime injections of BIAsp30 resulted in a significant reduction in HbA1C[HI vs. BIAsp30 (%, geometric mean and range): 8.6 (7.4-11.4) vs. 8.3 (6.7-9.8), p = 0.013]. During treatment with BIAsp30, nighttime glycaemic control was significantly improved. Day-to-day variation in pharmacodynamics and pharmacokinetics and the rate of hypoglycaemia were not increased with BIAsp30 compared with HI.

CONCLUSIONS

In type 1 diabetics, multiple mealtime administration of BIAsp30 compared with traditional basal-bolus human insulin treatment significantly improves long-term glycaemic control without increasing the risk of hypoglycaemia. Despite a higher proportion of intermediate-acting insulin, thrice-daily injections with BIAsp30 do not increase the day-to-day variations in insulin pharmacokinetics and pharmacodynamics.

Adsorption of human insulin and AspB28 insulin on a PTFE-like surface

The interactions of human insulin, Zn-free human insulin, and AspB28 insulin with a hydrophobic surface were studied by ellipsometry. All three insulin types investigated adsorbed with high affinity onto the hydrophobic surface, as the plateau of the adsorption isotherm, represented by the irreversible bound fraction, was reached at concentrations >10(-3) mg/ml. The plateau values for human insulin and Zn-free human insulin could not be distinguished with statistical significance, whereas the plateau value for AspB28 insulin was lower than those for the two others, with an adsorbed amount corresponding to a monolayer of insulin monomers. The results observed may be explained by differences in self-association patterns of the insulin types or by enhanced charge repulsion between the AspB28 analog and the negatively charged surface.

Within-patient variation of the pharmacokinetics of subcutaneously injected biphasic insulin aspart as assessed by compartmental modelling

AIMS/HYPOTHESIS

Pharmacokinetics of s.c. administered insulin preparations have been widely studied, mostly using descriptive measures such as AUC, time to peak, or the peak plasma concentration. Several compartmental modelling studies of single-bolus s.c. insulin pharmacokinetics have also appeared, with contrasting results regarding the feasibility of insulin pharmacokinetics modelling and the appropriate level of detail for such models. In this paper, we used compartmental models to study the pharmacokinetics of biphasic insulin aspart administered by multiple s.c. injections. The main objective was to assess the magnitude of the inter-and intra-subject variation in the kinetics.

MATERIALS AND METHODS

Analyses were performed on 24-h serum insulin concentrations measured in 20 type 1 diabetes subjects given three daily s.c. injections of biphasic insulin aspart.

RESULTS

Preliminary analysis of the AUC:dose ratio showed that the apparent kinetics are not constant throughout the three daily injections of the compound. A simple and robust compartmental model was shown to be appropriate for interpreting the observations, provided that one of its parameters (the first-order rate constant for transfer from the s.c. depot to plasma) is allowed to vary between injections.

CONCLUSIONS/INTERPRETATION

Population estimates of the chosen model show that intra-subject variations between injections is of the same order of magnitude as inter-subject variation, partially explaining the difficulties encountered when individually tailoring intensified insulin therapy. We conclude that the explicit consideration of a rather simple kinetic model will allow better experimental designs in the future study of s.c. insulin preparations.

Advantage of premeal-injected insulin glulisine compared with regular human insulin in subjects with type 1 diabetes

OBJECTIVE

Insulin glulisine, a rapid-acting insulin analog, provides prandial insulin replacement. In this study, we compared postprandial blood glucose control after pre- and postmeal insulin glulisine with regular human insulin (RHI).

RESEARCH DESIGN AND METHODS

In a single-dose, randomized, four-way complete cross-over study, subjects received standardized, 15-min meals, covered by subcutaneous injections of either insulin glulisine (immediately premeal or 15 min postmeal; 0.15 unit/kg per injection) or RHI (30 min or immediately premeal; 0.15 unit/kg per injection). Twenty-one patients with type 1 diabetes (mean age 36.4 years; mean BMI 26.0 kg/m(2)) were enrolled; 20 patients completed the study. Postprandial baseline-subtracted blood glucose exposure, maximum excursion, maximum and minimum blood glucose concentrations, and time to the maximum excursion and minimum concentration were assessed, along with serum insulin concentrations.

RESULTS

Lower maximum blood glucose excursion (65 vs. 89 mg/dl), total blood glucose exposure within 2 h (279 vs. 334 mg . h/dl, maximum blood glucose concentration (180 vs. 209 mg/dl), and less time to maximum blood glucose excursion (48 vs. 70 min) were seen with immediately premeal insulin glulisine versus immediately premeal RHI. The maximum serum concentration of insulin glulisine was almost double that of RHI (82 vs. 45 microU/ml), achieved in approximately half the time (55 vs. 97 min). Conversely, insulin glulisine (15 min postmeal) versus RHI (immediately premeal) and RHI (30 min premeal) versus insulin glulisine (immediately premeal) resulted in comparable blood glucose control.

CONCLUSIONS

Insulin glulisine renders postprandial glucose disposal closer to physiologic requirements compared with RHI and enables appropriate timing of prandial insulin administration.

Basal-Prandial Insulin Therapy: Scientific Concept Review and Application

The majority of patients with type 2 diabetes mellitus (T2DM) eventually require the addition of basal insulin to existing oral therapy to achieve the glycemic goals set forth by the American Diabetes Association (A1C, <7.0%). In many patients with T2DM, insulin is the only option for achieving glycemic control and may be used successfully to attain glycemic targets in regimens that combine basal insulin with oral antidiabetic agents, or in regimens that combine basal insulin with mealtime (prandial) insulin. Basal-prandial insulin regimens that use a long-acting insulin analogue to control the fasting plasma glucose level and a short-acting insulin analogue for post-meal glucose excursions replace insulin in a manner that most closely approximates normal physiologic patterns. The current body of evidence demonstrates that such regimens will prove to be the optimal strategy for achieving glycemic control in patients with T2DM who require both basal and prandial insulin replacement. Here, we review current findings in the published literature on the efficacy of basal-prandial insulin, with a focus on practical information that might help to provide an evidence-based guide for progressing to basal-prandial insulin therapy in appropriate patients with T2DM.

Study of the insulin dimerization: binding free energy calculations and per-residue free energy decomposition

A calculation of the binding free energy for the dimerization of insulin has been performed using the molecular mechanics-generalized Born surface area approach. The calculated absolute binding free energy is -11.9 kcal/mol, in approximate agreement with the experimental value of -7.2 kcal/mol. The results show that the dimerization is mainly due to nonpolar interactions. The role of the hydrogen bonds between the 2 monomers appears to give the direction of the interactions. A per-atom decomposition of the binding free energy has been performed to identify the residues contributing most to the self association free energy. Residues B24-B26 are found to make the largest favorable contributions to the dimerization. Other residues situated at the interface between the 2 monomers were found to make favorable but smaller contributions to the dimerization: Tyr B16, Val B12, and Pro B28, and to an even lesser extent, Gly B23. The energy decomposition on a per-residue basis is in agreement with experimental alanine scanning data. The results obtained from a single trajectory (i.e., the dimer trajectory is also used for the monomer analysis) and 2 trajectories (i.e., separate trajectories are used for the monomer and dimer) are similar.

Nanoscale analysis of protein and peptide absorption: insulin absorption using complexation and pH-sensitive hydrogels as delivery vehicles

Recent advances in the discovery and delivery of drugs to cure chronic diseases are achieved by combination of intelligent material design with advances in nanotechnology. Since many drugs act as protagonists or antagonists to different chemicals in the body, a delivery system that can respond to the concentrations of certain molecules in the body is invaluable. For this purpose, intelligent therapeutics or "smart drug delivery" calls for the design of the newest generation of sensitive materials based on molecular recognition. Biomimetic polymeric networks can be prepared by designing interactions between the building blocks of biocompatible networks and the desired specific ligands and by stabilizing these interactions by a three-dimensional structure. These structures are at the same time flexible enough to allow for diffusion of solvent and ligand into and out of the networks. Synthetic networks that can be designed to recognize and bind biologically significant molecules are of great importance and influence a number of emerging technologies. These synthetic materials can be used as unique systems or incorporated into existing drug delivery technologies that can aid in the removal or delivery of biomolecules and restore the natural profiles of compounds in the body.

Loading and mobility of spin-labeled insulin in physiologically responsive complexation hydrogels intended for oral administration

Poly(methacrylic acid-g-ethylene glycol) copolymers are pH-responsive complexation hydrogels that have shown promise in in vitro and in vivo results as oral insulin delivery carriers. With the aim of gaining more detailed insight into their performance to further improve the carriers, we spin-labeled insulin and used electron spin resonance (ESR) spectroscopy to follow the loading of the spin-labeled insulin into the copolymer microparticles. A flow through system was developed to monitor continuously and non-invasively the dynamics of the spin-labeled insulin and its surrounding microviscosity during release. Using these methods, the loading efficiency of insulin was determined and was found to match previous HPLC measurements. Additionally, the protein-friendly nature of the hydrogels was demonstrated. The monitoring of the dynamics during flow through provided a rationalization for the unwanted initial burst release in an acidic environment. These studies will aid in the optimization of the system, and will be a basis for subsequent in vivo ESR investigations.

Pre-meal insulin aspart compared with pre-meal soluble human insulin in type 1 diabetes

Insulin aspart has been shown, in medium-term studies, to achieve reductions in HbA(1c) without increasing the risk of major hypoglycaemia compared with pre-meal human insulin. The aim of the present 3-year study was to evaluate the long-term safety and efficacy of insulin aspart in people with type 1 diabetes. This was a 30-month extension of a multinational, multicentre, open-label, parallel-group study of 753 people with type 1 diabetes, originally randomly allocated to treatment with insulin aspart or unmodified human insulin before meals, with NPH insulin as basal insulin. Main outcomes measures were hypoglycaemia (major or minor), adverse events and HbA(1c). As insulin aspart became commercially available in some countries before the end of the trial, analyses of HbA(1c) used 30-month data to maintain statistical power. The relative risk estimate of major hypoglycaemia was similar between treatment groups (relative risk [RR] 1.00 [95% CI 0.72, 1.39]). The risk of having a minor hypoglycaemic episode was higher with insulin aspart than with human soluble insulin (RR 1.24 [1.09, 1.39] p=0.024). Insulin aspart was significantly superior to human insulin with respect to overall glycaemic control, with a baseline-adjusted HbA(1c) difference of -0.16 (-0.32, -0.01)% (p=0.035). Insulin aspart was well tolerated and effective during long-term treatment. The HbA(1c) advantage was maintained with insulin aspart without any adverse impact on the rate of major hypoglycaemia.

Pharmacologic modifications of hormones to improve their therapeutic potential for diabetes management

Rapid-acting genetically engineered insulin analogues emerging in the last 10 years are now established as more effective prandial insulins than traditional short-acting human insulin. The development of analogues for use as basal insulin, however, has been much slower. Methods of pro-tracting the time-action curve of injected insulin include complexing with proteins, insulin crystal formation, shifting the iso-electric point of the amino acid sequence or attaching a fatty-acid side chain to the molecule. The latter two methods have been more successful in producing physiologic insulin profiles when compared with the former methods. The principle of acylation has also been applied to prolong the action of other hormones, such as glucagon-like peptide 1 (GLP-1), as the native peptide has a very short half-life. Preliminary results with this compound and other GLP-1 analogues show promise in treating patients with type 2 diabetes. In summary, the development of new insulin and other hormone preparations by the manipulation of native peptide structure has recently improved our antidiabetic armamentarium, and further research will continue this fruitful approach.

Quantitative estimation of the effects of bile salt surfactant systems on insulin stability and permeability in the rat intestine using a mass balance model

The oral delivery of peptides and proteins is compromised by chemical and proteolytic instability as well as by permeability limitations. The aim of this study was to delineate the relative contributions of simple bile salt and bile salt:fatty acid mixed micellar systems to protein stability vs permeability enhancement in the rat intestine. Insulin disappearance from the rat intestine was evaluated when administered in simple micellar systems of sodium cholate (NaC), sodium taurocholate (NaTC) and sodium glycocholate (NaGC), and in mixed micellar systems of these bile salts and linoleic acid (LA). In-vitro stability studies were used to evaluate the extent of insulin degradation in the different micellar systems. After correction for insulin degradation in all systems a mass balance model was used to estimate the fractions of insulin absorbed for all systems. Mass balance estimates for the extent of insulin absorption in control perfusion systems were consistent with previously reported predictions of the model for ileal insulin absorption. Mass balance estimates for NaGC suggested no significant effects on the fraction of insulin absorbed relative to control. However, insulin absorption was estimated to occur to a significantly greater extent for NaTC simple micellar systems and was coincident with increased permeability of the hydrophilic marker molecule PEG 4000. The mass balance model estimated higher fractions of insulin absorbed for all mixed micellar systems in line with enhanced plasma insulin levels and higher PEG 4000 permeabilities for these systems.