Two cheers for inhaled insulin

Needle-free jet injection of rapid-acting insulin improves early postprandial glucose control in patients with diabetes

OBJECTIVE

Clamp studies have shown that the absorption and action of rapid-acting insulin are faster with injection by a jet injector than with administration by conventional pen. To determine whether these pharmacokinetic changes also exist in patients with diabetes and benefit postprandial glucose control, we compared the pharmacologic profiles of insulin administration by jet injection versus conventional insulin pen after a standardized meal in patients with type 1 or type 2 diabetes.

RESEARCH DESIGN AND METHODS

In a randomized, double-blind, double-dummy crossover study, 12 patients with type 1 diabetes and 12 patients with type 2 diabetes received insulin aspart either by jet injection or by conventional pen, in both cases followed by a standardized meal. Blood was sampled for 6 h for determination of glucose and insulin levels to calculate pharmacologic profiles.

RESULTS

Insulin administration by jet injection resulted in shorter time until peak plasma insulin level (51.3 ± 6.4 vs. 91.9 ± 10.2 min; P = 0.003) and reduced hyperglycemic burden during the first hour (154.3 ± 20.8 vs. 196.3 ± 18.4 mmol · min · L(-1); P = 0.041) compared with conventional administration. Jet injection did not, however, significantly reduce the hyperglycemic burden during the 5-h period thereafter. There was no indication that the jet injector performed differently in patients with type 1 and type 2 diabetes.

CONCLUSIONS

The considerably more rapid insulin absorption after administration by jet injector translated to a significant if modest decrease in postprandial hyperglycemia in patients with type 1 and type 2 diabetes. The improved early postprandial glucose control may specifically benefit patients who have difficulty in limiting postprandial glucose excursions.

Preparation, characterization and in vivo evaluation of pH-sensitive oral insulin-loaded poly(lactic-co-glycolicacid) nanoparticles

AIM

Oral administration of insulin is a promising drug delivery system for diabetic patients as it is convenient and reduces pain, two of the major contributors to non-compliance.

METHODS

In this study, insulin was encapsulated in poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) by using double-emulsion/solvent evaporation technique and analyses on its release kinetics were carried out using both in vitro and in vivo methods.

RESULTS

First, only by this simple methods, release speed of insulin from NPs can be controlled in different pH solution. The rate of release of insulin was found to be slower in acidic pH; about 90% of insulin was released in 11 days at pH 1.0. In alkaline conditions, the release was faster; about 90% release was observed to occur within 3 days at pH 7.8. The insulin-loaded poly (lactic-co-glycolic acid) nanoparticles (PINPs) were administered orally to diabetes mellitus-induced rats and the response of blood glucose and insulin levels was estimated. Blood glucose decreased and the concentration of insulin in animal blood increased. In diabetic animals which were administered intermittent insulin, every 8 h, blood glucose levels were maintained equivalently with those of healthy rats.

CONCLUSION

These experimental results indicated that oral PINPs are able to deliver insulin effectively and decrease animal blood sugar; in conclusion, this may be a promising delivery system for the treatment of diabetes.

Encapsulation of insulin–cyclodextrin complex in PLGA microspheres: a new approach for prolonged pulmonary insulin delivery

The insulin administration by pulmonary route has been investigated in the last years with good perspectives as alternative for parenteral administration. However, it has been reported that insulin absorption after pulmonary administration is limited by various factors. Moreover, in the related studies one daily injection of long-acting insulin was necessary for a correct glycemic control. To abolish the insulin injection, the present study aimed to develop a new formulation for prolonged pulmonary insulin delivery based on the encapsulation of an insulin:dimethyl-beta-cyclodextrin (INS:DM-beta-CD) complex into PLGA microspheres. The molar ratio of insulin/cyclodextrin in the complex was equal to 1:5. The particles were obtained by the w/o/w solvent evaporation method. The inner aqueous phase of the w/o/w multiple emulsion contained the INS:DM-beta-CD complex. The characteristics of the INS:DM-beta-CD complex obtained were assessed by 1H-NMR spectroscopy and Circular Dichroism study. The average diameter of the microspheres prepared, evaluated by laser diffractometry, was 2.53 +/- 1.8 microm and the percentage of insulin loading was 14.76 +/- 1.1. The hypoglycemic response after intratracheal administration (3.0 I.U. kg(-1)) of INS:DM-beta-CD complex-loaded microspheres to diabetic rats indicated an efficient and prolonged release of the hormone compared with others insulin formulations essayed.

Insulin structure and function

Throughout much of the last century insulin served a central role in the advancement of peptide chemistry, pharmacology, cell signaling and structural biology. These discoveries have provided a steadily improved quantity and quality of life for those afflicted with diabetes. The collective work serves as a foundation for the development of insulin analogs and mimetics capable of providing more tailored therapy. Advancements in patient care have been paced by breakthroughs in core technologies, such as semisynthesis, high performance chromatography, rDNA-biosynthesis and formulation sciences. How the structural and conformational dynamics of this endocrine hormone elicit its biological response remains a vigorous area of study. Numerous insulin analogs have served to coordinate structural biology and biochemical signaling to provide a first level understanding of insulin action. The introduction of broad chemical diversity to the study of insulin has been limited by the inefficiency in total chemical synthesis, and the inherent limitations in rDNA-biosynthesis and semisynthetic approaches. The goals of continued investigation remain the delivery of insulin therapy where glycemic control is more precise and hypoglycemic liability is minimized. Additional objectives for medicinal chemists are the identification of superagonists and insulins more suitable for non-injectable delivery. The historical advancements in the synthesis of insulin analogs by multiple methods is reviewed with the specific structural elements of critical importance being highlighted. The functional refinement of this hormone as directed to improved patient care with insulin analogs of more precise pharmacology is reported.

Current challenges in non-invasive insulin delivery systems: a comparative review

The quest to eliminate the needle from insulin delivery and to replace it with non- or less-invasive alternative routes has driven rigorous pharmaceutical research to replace the injectable forms of insulin. Recently, various approaches have been studied involving many strategies using various technologies that have shown success in delivering insulin, which are designed to overcome the inherent barriers for insulin uptake across the gastrointestinal tract, mucosal membranes and skin. This review examines some of the many attempts made to develop alternative, more convenient routes for insulin delivery to avoid existing long-term dependence on multiple subcutaneous injections and to improve the pharmacodynamic properties of insulin. In addition, this article concentrates on the successes in this new millennium in developing potential non-invasive technologies and devices, and on major new milestones in modern insulin delivery for the effective treatment of diabetes.

Inhaled insulin

Inhaled insulin has attractive pharmacodynamic properties with a fast onset of action which should lead to improved postprandial blood glucose concentrations. Comparisons with regular subcutaneous (sc) insulin in clinical studies, however, showed lower fasting blood glucose concentrations. Overall, clinical efficacy of inhaled insulin was comparable to that of regular sc insulin. Treatment with inhaled insulin was safe and well tolerated, with slight and reversible changes in lung function parameters and a rise in insulin antibodies (not associated with any clinical or safety parameters) as main adverse effects. Treatment satisfaction in open-label studies was higher with inhaled than with sc insulin, indicating that inhaled insulin might help to overcome one of the major hurdles of diabetes therapy, i.e. a timely initiation of insulin therapy. The first inhaled insulin formulation was approved in the US and Europe in January 2006, but some countries granted reimbursement only for selected patients, or did not reimburse treatment with inhaled insulin at all because of the high treatment costs. These are due to the rather low bioavailability of approximately 8-15%. Therefore, further research is needed to improve the bioavailability of inhaled insulin: e.g. through optimization of the inhaler, the insulin formulation, or the inhalation technique. In view of the potential for further improvement, inhaled insulin may become a very attractive alternative to sc insulin, in particular in patients in whom insulin therapy has to be initiated and/or intensified.

Inhaled human insulin (Exubera): a review of its use in adult patients with diabetes mellitus

Inhaled human insulin (Exubera) (insulin human [rDNA origin]) Inhalation Powder) has recently been approved in the European Union and the US for preprandial use in adult patients with diabetes mellitus. This formulation of insulin has a more rapid onset, but similar duration, of glucose-lowering activity compared with subcutaneously administered regular human insulin. Preprandial inhaled human insulin provided glycaemic control that was comparable to preprandial subcutaneous regular insulin when added to long- or intermediate-acting subcutaneous basal insulin in patients with type 1 diabetes mellitus. Inhaled human insulin is also effective when administered alone, when combined with oral antihyperglycaemic therapy, or when combined with basal subcutaneous insulin in patients with type 2 diabetes mellitus. Comparable rates of hypoglycaemia occurred in patients treated with inhaled human insulin and in those treated with subcutaneous regular human insulin. Patients treated with inhaled human insulin demonstrated a greater decline in pulmonary function (forced expiratory volume in 1 second [FEV(1)], carbon monoxide diffusing capacity [DL(CO)]) than patients treated with comparator antihyperglycaemic agents; the mean difference between the treatment groups that favoured the comparators was noted within the first several weeks of treatment, and did not change over a 2-year treatment period. This agent has also been associated with significant improvements in some quality-of-life and treatment satisfaction scores, especially when compared with subcutaneous mealtime insulin regimens. Inhaled human insulin is an effective and well tolerated formulation suitable for preprandial use in combination with basal subcutaneous insulin in patients with type 1 diabetes. It is also well tolerated and effective in patients with type 2 diabetes when administered alone, when combined with oral antihyperglycaemic therapy, or when combined with basal subcutaneous insulin.

New strategies in insulin treatment: analogues and noninvasive routes of administration

Abstract Recent years have seen the development of alternatives to human insulin for the treatment of diabetes. Both rapid-acting and long-acting analogues are available. Alternative routes of insulin administration are emerging. The present review briefly summarizes the present knowledge on insulin analogues and alternative administration routes.

Inhaled Insulins

The inhalation of insulin was conceptualized by the mid-1920s, but the first successful testing of inhaled insulin occurred in the mid-1990s. The lung has proven to be an organ well capable of absorbing insulin in a reproducible and dose-dependent manner. At present, two concepts of pulmonary insulin delivery at relatively advanced stages of development have been investigated in several published studies. The first involves the Exubera device, a system consisting of a formulation of insulin in a dry and amorphous powder, which is then packaged into blisters. A special delivery system generates a pulse of compressed air, which causes the insulin to form a white fog in a transparent reservoir that can be inhaled by deep breathing. The second approach is the AERx insulin Diabetes Management System, which uses an aqueous formulation of insulin, delivered as an aerosol generated by a special, microprocessor-controlled, inhalation device. This device is capable of monitoring the patient's inspiratory flow and guiding the inhalation by a microelectronic feedback system. The therapeutic efficacy and safety of these inhaled insulins seem comparable to those of subcutaneous insulin regimens; however, inhaled insulins do not appear to achieve significantly better glycemic control. Several other concepts for the pulmonary delivery of insulin are also being developed. With the incidence of diabetes mellitus, especially type 2 diabetes, dramatically increasing worldwide, patients with type 2 diabetes appear to be an important target group for new modalities of insulin delivery. In this group, the onset of insulin treatment is frequently delayed due to the fear of self-injection, preventing effective glycemic control. Patient acceptance of inhaled insulins is excellent and no serious adverse effects have been observed to date. Further advantages of inhaled insulins are the more rapid onset of insulin action and a mitigation of postprandial glucose excursions. However, there are some open questions. The most important concerns the possible long-term effects of insulin inhalation on the lung, as insulin is known to have growth-promoting properties. Thus far, there are no observations of the effects of inhaled insulin on lung structure and function that extend beyond 10 years. In patients with pulmonary disease, the smaller cumulative alveolar surface may cause problems in absorption, and in smokers the action of inhaled insulin has been shown to be stronger and with a faster onset. Furthermore, treatment with inhaled insulin requires larger doses of insulin compared with the subcutaneous route of insulin administration to achieve the same systemic effect, and the costs of this therapy could therefore be significantly higher than the costs of present insulin therapies.

Alternative routes of insulin delivery

Attempts at replicating physiological insulin secretion, as a means of restoring the normal metabolic milieu and thereby minimizing the risk of diabetic complications, has become an essential feature of insulin treatment. However, despite advances in the production, purification, formulation and methods of delivery of insulin which have occurred in recent years, this has met with limited success. The current advocacy of intensive insulin therapy regimens involving multiple daily subcutaneous injection places a heavy burden of compliance on patients and has prompted interest in developing alternative, less invasive routes of delivery. To date, attempts to exploit the nasal, oral, gastrointestinal and transdermal routes have been mainly unsuccessful. The respiratory tree, with a large surface area, offers the greatest potential for the delivery of polypeptide drugs and there is renewed interest in administrating insulin by the intrapulmonary route. Current pulmonary drug delivery systems include a variety of pressurized metered dose inhalers, dry powder inhalers, nebulizers and aqueous mist inhalers. Recent clinical studies suggest a possible role for inhaled insulin in fulfilling meal-related insulin requirements in persons with Type 1 and Type 2 diabetes. Most experience with inhaled insulin has been obtained using either dry powder formulation in the Nektar Pulmonary Inhaler/Exubera device (Nektar Therapeutics Inc., San Carlos, CA, Aventis, Bridgewater, NJ, Pfizer, NY) or a liquid aerosol formulation in the AERx Insulin Diabetes Management System (Aradigm Corp., Hayward, CA, NovoNordisk A/S, Copenhagen, Denmark). If long-term safety and efficacy is confirmed, inhalation may become the first non-subcutaneous route of insulin administration for widespread clinical use. Despite overwhelming interest and investment in administering insulin via the oral route, success is not expected in the short term. Attempts at utilizing the buccal mucosa and skin are also continuing. Pancreatic transplantation will remain limited to those patients receiving a kidney transplant and immunotherapy. Islet cell transplantation is at an early though encouraging stage following the availability of new less toxic immunosuppressive agents. True insulin independence will require further advances in the combined fields of cell biology and genetics to ensure freedom from both the need for lifelong administration of insulin and the complications of diabetes.

Inhaled insulin for the treatment of diabetes: projects and devices

A non-invasive alternative to insulin injections would represent a major improvement for Type 1 and 2 insulin-treated patients. The lung is the only route which allows bio-availability of insulin, approaching 10% without absorption enhancers. However, the reproducibility of the plasma response to the pulmonary insulin is similar to subcutaneous insulin analogues, that is to say, relatively poor. In the Exubera Project, the device is a dry powder inhaler. The insulin powder (Aventis) is packaged into a single dose blister containing 1 or 3 mg; the 1 mg blister corresponding to approximately 3 U of insulin. Phase II studies have shown similar efficacy than regular insulin. Data are available on 328 Type 1 and 309 Type 2 patients after 6 months of Phase III trials. The inhaled insulin group developed increased insulin antibodies. A total of 25% of the patients experienced cough after inhalation. The number of overall and severe hypoglycaemic episodes were similar in the two groups. Pulmonary function tests remained stable and normal except for minor reductions of carbon monoxide diffusion capacity. The AERx IDMS system is a microprocessor-controlled, aqeous mist inhaler. The insulin (regular 100 U/ml, Novo Nordisk) is delivered by 1 U increments. The clinical experience reported with this system so far is limited to 107 Type 2 insulin-treated patients. The results are similar to those obtained in the Exubera trials. In the Alkermes project, large, porous, regular insulin of low-mass density have been developed by the Advanced Inhalation Project. Results from human studies in normal subjects show similar pharmacokinetics as the two other devices above. Other projects seem less advanced than the projects cited above e.g., Aerodos and Oralin. Current clinical experience with inhaled insulin seems promising. It represents currently the only viable non-invasive alternative to insulin injections. However, long-term local tolerance of the pulmonary tissue is a crucial issue.

Novel drug delivery systems for insulin: clinical potential for use in the elderly

Diabetes mellitus is a very common disease in the elderly and its complications are responsible for excess morbidity/mortality, loss of independence and impaired quality of life. Recent studies, while not performed in the elderly, have outlined the importance of achieving tight glycaemic control in order to prevent complications. Eighty years after its discovery, subcutaneous insulin remains a major treatment for diabetes. It is used as a first-line agent in type 1 diabetes, and in type 2 diabetes when oral antihyperglycaemic agents combined with diet and exercise fail to achieve an appropriate metabolic control. To avoid injections, other routes of insulin administration have been studied, including oral, dermal and rectal routes but they were not found to be appropriate for clinical use. Buccal or nasal insulin combined with absorption enhancers proved to have interesting properties. Inhaled insulin appears to be suitable for use in patients with diabetes because of its better bioavailability and a pharmacokinetic profile that mimics the time kinetics of insulin secretion after a meal. Clinical studies were conducted among small numbers of patients with type 1 or type 2 diabetes who had been treated with subcutaneous insulin. Inhaled insulin was given three times daily, just before meals, and was combined with a bedtime subcutaneous injection of long-acting insulin. In patients with type 1 or type 2 diabetes the metabolic control achieved with inhaled insulin was similar to that obtained with a subcutaneous insulin regimen. Tolerance of inhaled insulin was good and treatment satisfaction was better than that with the subcutaneous regimen. Insulin inhalation appears to be an interesting way of insulin delivery for elderly patients with diabetes. However, no studies have been conducted in elderly patients with diabetes to assess this route's acceptability, convenience and ease of use in this particular population. In addition, it is necessary to conduct pharmacokinetic studies in the elderly because lung aging might reduce the bioavailability of inhaled insulin.

Pharmacotherapy of diabetes mellitus: implications for the prevention and treatment of cardiovascular disease

Diabetes mellitus in adults is associated with an increased risk of premature vascular disease and a higher mortality rate. The presence of other risk factors, often seen in diabetic patients, such as systemic hypertension, augments the rate of vascular diseases. Evidence is growing that tight control of hyperglycemia using insulin and/or oral hypoglycemic agents will modify this risk. More aggressive control of concomitant hypertension and/or hyperlipidemia is also required. Diabetic patients who have myocardial infarctions do worse than nondiabetic patients. Various strategies to improve outcomes include the use of tight blood glucose control, and various coronary interventions are currently under clinical study.

Hypothesis: can glucose-insulin-potassium regimen in combination with polyunsaturated fatty acids suppress lupus and other inflammatory conditions?

In systemic lupus erythematosus, plasma concentrations of tumor necrosis factor alpha (TNF alpha) and other pro-inflammatory cytokines are elevated and those of transforming growth factor beta (TGF beta) are decreased. TNF alpha prevents lupus nephropathy whereas increased concentration of TGF beta causes glomerulosclerosis. Insulin inhibits TNF alpha and enhances TGF beta production, augments nitric oxide synthesis and blocks superoxide anion generation. Polyunsaturated fatty acids (PUFAs) also have actions similar to insulin. Hence, it is suggested that a combination of insulin (in the form of glucose-insulin-potassium) and PUFAs may be of benefit in lupus and other inflammatory conditions.