The role of rapid-acting insulin analogues and inhaled insulin in type 2 diabetes mellitus

sBackground:The availability of rapid-acting insulin analogues and inhaled insulin gives clinicians additional treatmentoptions in the management of patients with diabetes mellitus (DM). Combining rapid-acting insulin analogues with basal insulin can more closely mimic physiologic insulin release to maximize glycemic control.Objective:The objective of this article was to discuss the role of rapid-acting insulin analogues and inhaled insulin inthe treatment of patients with type 2 DM.Methods:Materials for this article were obtained through an online search of MEDLINE/PubMed and Google(1996-2006) using the search terms bolus insulin, postprandial, rapid-acting insulin analogues, titration, hypoglycemia, glycemic control, inhaled insulin, and insulins lispro, aspart, and glulisine.Results:Glycosylated hemoglobin (A1C) levels and number of all hypoglycemic episodes were similar in patients withtype 2 DM taking either mealtime rapid-acting insulin analogues or regular human insulin (RHI). Rapid-acting insulins have been successfully used in basal-bolus regimens with a variety of long- and intermediate-acting insulins, as well as with oral hypoglycemic agents. Injectable rapid-acting insulin analogues markedly decreased postprandial glucose (PPG) levels compared with RHI. Better reduction in PPG levels may be key to achieving target A1C levels in some patients, but long-term outcome studies are needed to assess whether lowering PPG levels decreases cardiovascular risk in patients with type 2 DM. Inhaled insulin may be an option for patients who cannot inject insulin, but route of administration and dosing issues limit its use in many patients. The effect of inhaled insulin on PPG is unclear at this time.Conclusions:Although rapid-acting insulin analogues are effective in the management of patients with type 2 DM, the limited numbers of studies have yet to demonstrate that these agents have any significant long-term advantage compared with RHI. In addition, they cost more than RHI. Further studies are needed to compare the efficacy of the rapid-acting insulin analogues, to compare the different dosing regimens used with mealtime insulin administration, and to ascertain if the decrease in PPG levels seen with the use of rapid-acting insulin analogues translates into improved glycemic control and perhaps even a reduction in cardiovascular risk in patients with type 2 DM. (Insulin. 2007;2:61-67) Copyright 2007 Excerpta Medica, Inc.     

Insulin analogues - state of the art

The use of insulin analogues is rapidly expanding. At present, there are two short-acting analogues available for practical use, insulin aspart and insulin lispro, and one long-acting analogue, insulin glargine. Another long-acting analogue, insulin detemir, is still under development. The time action profile of short-acting analogues is both much more rapid and shorter than that of human insulin; the prominent feature of the long-acting analogues is their peakfree and fairly constant action. Insulin analogues offer alternative options for the whole spectrum of insulin therapy in type 1 and type 2 diabetes patients. The perception by many patients is strikingly positive, in particular regarding the overall quality of life. In objective efficacy terms, however, the potential to improve the degree of metabolic control appears to be only minor, yet demonstrable, provided the analogues are used according to their specific time action profile. This ensured, analogues are instrumental in minimizing the side effects of insulin therapy, i.e. the risk of (nocturnal) hypoglycaemia or problems with body weight control. Although there are no indications of safety concerns with insulin analogues, the availability of long-term outcome data based upon observations in human patients would be very valuable.     

Cost-effectiveness of insulin analogues for diabetes mellitus

Background

Insulin analogues may be associated with fewer episodes of hypoglycemia than conventional insulins. However, they are costly alternatives. We compared the cost-effectiveness of insulin analogues and conventional insulins used to treat type 1 and type 2 diabetes mellitus in adults.

Methods

We conducted a cost-effectiveness evaluation of insulin analogues versus conventional insulins using the Center for Outcomes Research Diabetes Model. We compared rapid-acting analogues (insulin aspart and insulin lispro) with regular human insulin, and long-acting analogues (insulin glargine and insulin detemir) with neutral protamine Hagedorn insulin. We derived clinical information for the comparisons from meta-analyses of randomized controlled trials. We obtained cost and utility estimates from published sources. We performed sensitivity analyses to test the robustness of our results.

Results

For type 1 diabetes, insulin aspart was more effective and less costly than regular human insulin. Insulin lispro was associated with an incremental cost of Can$28 996 per quality-adjusted life-year. The incremental cost per quality-adjusted life-year was Can$87 932 for insulin glargine and Can$387 729 for insulin detemir, compared with neutral protamine Hagedorn insulin. For type 2 diabetes, insulin aspart was associated with an incremental cost of Can$22 488 per quality-adjusted life-year compared with regular human insulin. For insulin lispro, the incremental cost was Can$130 865. Compared with neutral protamine Hagedorn insulin, insulin detemir was less effective and more costly. Insulin glargine was associated with an incremental cost of Can$642 994 per quality-adjusted life-year. The model was sensitive to changes in the effect size of hemoglobin A_1c and to decrements applied to utility scores when fear of hypoglycemia was included as a factor.

Interpretation

The cost-effectiveness of insulin analogues depends on the type of insulin analogue and whether the patient receiving the treatment has type 1 or type 2 diabetes. With the exception of rapid-acting insulin analogues in type 1 diabetes, routine use of insulin analogues, especially long-acting analogues in type 2 diabetes, is unlikely to represent an efficient use of finite health care resources.Insulin agents available for the treatment of diabetes mellitus include conventional insulins and insulin analogues. Insulin analogues were developed to mimic more closely the separate bolus and basal components of insulin secretion.¹ Rapid-acting (bolus or mealtime) and long-acting (basal or background) analogue formulations are available. This new class of drugs has been promoted as providing more flexible treatment schedules and a reduced risk of hypoglycemia relative to conventional insulins.¹The cost of insulin analogues exceeds that of conventional insulins.^2,3 More than US$7.3 billion was spent globally on the purchase of insulin products in 2005 — an increase of 19% over the previous year.⁴ It has been suggested that the increased expenditure was due to both the increasing prevalence of diabetes and the increased use of insulin analogues.⁵We performed an analysis of the cost-effectiveness of insulin analogues compared with conventional insulins in the management of type 1 or type 2 diabetes in adults.     

Rapid-Acting Insulin Analogues in Basal-Bolus Regimens in Type 1 Diabetes Mellitus

ObjectiveTo compare rapid-acting insulin analogues with regular human insulin in terms of hemoglobin A_1c, hypoglycemia, and insulin dose when used in a basal-bolus regimen in patients with type 1 diabetes mellitus.MethodsMEDLINE and congress proceedings were searched for randomized controlled trials comparing pran- dial insulins in a basal-bolus regimen in adults or children/ adolescents with type 1 diabetes. Studies in pregnancy, ob- servational studies, studies that compared premixed insulin or continuous subcutaneous insulin infusion/insulin pumps, and studies where the basal insulin was also changed were excluded. Only studies reporting baseline-endpoint change in insulin dose, or baseline and/or endpoint values, were included.ResultsTwenty-eight studies were identified (insulin glulisine, 4; insulin aspart, 7; insulin lispro, 17). Twenty- five studies compared a rapid-acting insulin analogue with regular human insulin, and 3 trials compared 2 rapid-acting insulin analogues. Overall, rapid-acting insulin analogues in a basal-bolus regimen provided similar or greater im- provements in glycemic control than regular human insulin at similar insulin doses, as well as a lower incidence of hypoglycemia.ConclusionsResults of the studies identified in this literature review indicate that a basal-bolus regimen with prandial rapid-acting insulin analogue provides advan- tages over basal-bolus regimens using prandial regular hu- man insulin, providing improvements in glycemic control comparable to those obtained with regular human insulin, as well as a lower incidence of hypoglycemia. (Endocr Pract. 2010;16:486-505)     

Efficacy and safety of insulin analogues for the management of diabetes mellitus: a meta-analysis

Background

Although insulin analogues are commonly prescribed for the management of diabetes mellitus, there is uncertainty regarding their optimal use. We conducted meta-analyses to compare the outcomes of insulin analogues with conventional insulins in the treatment of type 1, type 2 and gestational diabetes.

Methods

We updated 2 earlier systematic reviews of the efficacy and safety of rapid-and long-acting insulin analogues. We searched electronic databases, conference proceedings and “grey literature” up to April 2007 to identify randomized controlled trials that compared insulin analogues with conventional insulins. Study populations of interest were people with type 1 and type 2 diabetes (adult and pediatric) and women with gestational diabetes.

Results

We included 68 randomized controlled trials in the analysis of rapid-acting insulin analogues and 49 in the analysis of long-acting insulin analogues. Most of the studies were of short to medium duration and of low quality. In terms of hemoglobin A_1c, we found minimal differences between rapid-acting insulin analogues and regular human insulin in adults with type 1 diabetes (weighted mean difference for insulin lispro: –0.09%, 95% confidence interval [CI] –0.16% to –0.02%; for insulin aspart: –0.13%, 95% CI –0.20% to –0.07%). We observed similar outcomes among patients with type 2 diabetes (weighted mean difference for insulin lispro: –0.03%, 95% CI –0.12% to –0.06%; for insulin aspart: –0.09%, 95% CI –0.21% to 0.04%). Differences between long-acting insulin analogues and neutral protamine Hagedorn insulin in terms of hemoglobin A_1c were marginal among adults with type 1 diabetes (weighted mean difference for insulin glargine: –0.11%, 95% CI –0.21% to –0.02%; for insulin detemir: –0.06%, 95% CI –0.13% to 0.02%) and among adults with type 2 diabetes (weighted mean difference for insulin glargine: –0.05%, 95% CI –0.13% to 0.04%; for insulin detemir: 0.13%, 95% CI 0.03% to 0.22%). Benefits in terms of reduced hypoglycemia were inconsistent. There were insufficient data to determine whether insulin analogues are better than conventional insulins in reducing long-term diabetes-related complications or death.

Interpretation

Rapid-and long-acting insulin analogues offer little benefit relative to conventional insulins in terms of glycemic control or reduced hypoglycemia. Long-term, high-quality studies are needed to determine whether insulin analogues reduce the risk of long-term complications of diabetes.Diabetes mellitus is associated with serious long-term complications and premature death.¹ Data from the Health Canada National Diabetes Surveillance System indicate that, in 2004/05, diabetes was diagnosed in about 5.5% (1.8 million) of Canadians aged 20 years and older.² Because the disease goes undetected in many cases, the true prevalence may approach 1.9 million.³Tight glycemic control, to maintain a hemoglobin A_1c concentration of 7.0% or less, is recommended for all patients with diabetes to reduce the risk of long-term complications such as cardiovascular-related death, retinopathy and nephropathy.⁴ Insulin is indicated for all patients with type 1 diabetes and for patients with type 2 diabetes if adequate glycemic control cannot be achieved through exercise, diet or oral antidiabetic therapy.⁴Conventional insulins include regular human insulin and intermediate-acting neutral protamine Hagedorn insulin. However, these agents do not replicate the pattern of basal and postprandial endogenous secretion of insulin. Insulin analogues are modified human insulins developed to address this limitation.⁵ The rapid-acting insulin analogues insulin lispro, insulin aspart and insulin glulisine are marketed in Canada as bolus insulins; the long-acting agents insulin glargine and insulin detemir are marketed as basal insulins.⁶Systematic reviews of the insulin analogues have been published previously.^7–10 However, through our comprehensive search of the literature, we did not identify any reviews of long-acting insulin analogues in the management of type 1 diabetes or gestational diabetes. In this article, we provide an up-to-date, comprehensive systematic review and meta-analysis of outcomes associated with the use of rapid-and long-acting insulin analogues in type 1 and type 2 diabetes (adult and pediatric patients) and gestational diabetes. Detailed methods and complete results are reported elsewhere.^11,12     

Seguridad de los análogos de insulina: qué evaluar,cómo hacerlo y cómo interpretar los resultados

The widespread use of insulin analogues is based not only on the pharmacokinetics of these preparations, which is much closer to the physiology of insulin secretion under normal conditions, but also on their safety and effectiveness. The publication of a possible association between the use of a long-acting insulin analogue (glargine) and breast cancer has caused uneasiness among the medical community regarding the safety of these analogues.The mechanism of increased tumor activity of insulin analogues is explained by the fact that they act through insulin receptors (IR) and insulin-like growth factor-1 (IGF-1R), stimulating cell growth and inhibiting apoptosis. There are two major mechanisms: an increase in the binding time of insulin to IR and increased activation of IGF-1R. Therefore, to evaluate the safety of an analogue, the slower dissociation rate from its insulin receptor must be excluded, as well as the increased affinity for the IGF-1 receptor. This is equivalent to an index of mitogenic/metabolic activity of less than 1. These aspects can only be evaluated through study of cell lines and animal testing, which are reductionist models that cannot always be extrapolated to humans. To date, there are no data to question the safety of insulin analogues in general. However, the results of observational studies and some in vitro studies, suggesting a potential risk of mitogenicity with the administration of glargine, have caused some alarm among the medical community. Until now, there are no data to refute or confirm this risk and, therefore, evaluation of the existing data is crucial to obtain objective information.     

Analogues et dosages d’insuline : le cas général et le cas particulier de la glargine

Since 1996, genetic engineering has allowed modifications of insulin yielding to multiple modified insulins with different pharmacokinetic and/or pharmacodynamic properties. Molecules with maintained pharmacodynamic and modified pharmacokinetic profiles have been selected. Currently available rapid-acting analogues (lispro, aspart and glulisine) achieve plasma peak concentrations about twice as high and within approximately half the time compared with regular human insulin thus closely mimicking the physiological insulin response to a meal. Long-acting analogues (glargine and detemir) ensure the steady supplement of basal insulin plasma levels, with a plateau type of profile. Main analytical pitfalls of commercially human insulin immunoassays include crossreactivity with analogues and their metabolites. These crossreactivities are of great concern for interpreting insulin levels in patients treated with analogues. The development of more specific analytical methods to quantify separately the concentrations of endogenous insulin, rapid-acting and long-acting analogues and metabolites would be of utmost importance: (1) to further understand long-acting analogue variability in terms of efficiency; (2) to perform analogue kinetic studies; (3) to measure analogues in routine toxicology (forensic medicine) and (4) to assess intact glargine or glargine metabolite in vivo toxicity: recent debates about glargine safety have highlighted the lack of data about metabolite status (proportion of metabolized glargine and bioactivity of its metabolite). This goal could be achieved by specific immunoassay development or/and mass spectrometry analysis.     

Superiority of insulin analogues versus human insulin in the treatment of diabetes mellitus

The modern goals of insulin replacement in Type 1 and Type 2 diabetes mellitus (T1, T2DM) are A1C <6.5% long-term, and prevention of hypoglycaemia (blood glucose, BG <70 mg/dl). In addition to appropriate education and motivation of diabetic subjects, the use of rapid- and long-acting insulin analogues, is critical to achieve these goals. The benefits of rapid-acting analogues (lispro, aspart and glulisine have similar pharmacodynamic effects) compared with non-modified human regular insulin, are: (a) lower 1- and 2-h post-prandial blood glucose; (b) lower risk of late post-prandial hypoglycaemia (and therefore lower BG variability); (c) better quality of life (greater flexibility in timing and dosing of insulin). In T1DM, rapid-acting analogues improve A1C only by the extent to which replacement of basal insulin is optimized at the same time, either by multiple daily NPH administrations, or continuous subcutaneous insulin infusion (CSII), or use of the long-acting insulin analogues glargine or detemir. In T2DM, rapid-acting analogues reduce post-prandial hyperglycaemia more than human regular insulin, but systematic studies are needed to examine the effects on A1C. The benefits of long-acting insulin analogues glargine and detemir vs. NPH, are: (1) lower fasting BG combined with lower risk of hypoglycaemia in the interprandial state (night); (2) lower variability of BG. Glargine and detemir differ in terms of potency and duration of action. Detemir should be given twice daily in the large majority of people with T1DM, and in a large percentage of subjects with T2DM as well, usually at doses greater vs those of the once daily glargine. However, when used appropriately for individual pharmacokinetics and pharmacodynamics, glargine and detemir result into similar effects on BG, risk of hypoglycaemia and A1C. Rapid- and long-acting insulin analogues should always be combined in the treatment of T1 and T2DM.     

Use of recombinant human hyaluronidase to accelerate rapid insulin analogue absorption: experience with subcutaneous injection and continuous infusion

ObjectiveTo discuss clinical studies in which recombinant human hyaluronidase (rHuPH20) was used to increase insulin dispersion and accelerate its absorption.MethodsWe reviewed 10 pertinent clinical studies, 8 of which had data available.ResultsIn 4 euglycemic clamp studies, coinjection of rHuPH20 consistently yielded acceleration of insulin absorption, providing twice the insulin exposure during the first hour, greater and earlier peak exposure, and half the exposure beyond 2 hours after injection. Insulin-action profiles were similarly accelerated, with a 15-minute faster onset of insulin action and a 45-minute shorter duration of action for each of the 3 commercial rapid-acting insulin analogues. Infusion aspart insulin formulated with rHuPH20 also accelerated insulin absorption and action over the infusion set life when delivered by insulin pump. Administration of rHuPH20 reduced the inconsistency of insulin absorption and action profiles attributable to 3 factors—lack of reproducibility after identical injections, differences across insulin dose ranges, and changes over infusion site life. The rHuPH20-facilitated ultrafast profile consistently reduced hyperglycemic excursions both in injections immediately preceding liquid test meals and in bolus infusions immediately before solid test meals. rHuPH20-facilitated insulin administration has been well tolerated, with safety and tolerability similar to those with the comparator insulin alone.ConclusionrHuPH20 accelerates insulin-action profiles to an extent comparable to the difference between rapid-acting insulin analogue profiles and those of regular insulin. Studies are currently under way to characterize the effect on diabetes management end points (including hemoglobin A₁, blood glucose, and rates of hyperglycemia) of insulin analogues coformulated with rHuPH20 for treatment of both type 1 and type 2 diabetes. (Endocr Pract. 2011;17:914-921)     

Biological activity of GLP-1-analogues with N-terminal modifications

Glucagon-like peptide-1 (GLP-1) stimulates insulin secretion and improves glycemic control in type 2 diabetes. In serum the peptide is degraded by dipeptidyl peptidase IV (DPP IV). The resulting short biological half-time limits the therapeutic use of GLP-1. Therefore, various GLP-1 analogues with alterations in cleavage positions were synthesized. GLP-1-receptor binding was investigated in RINm5F cells. Biological activity of the GLP-1 analogues was investigated in vitro by measuring cAMP production in RINm5F cells. GLP-1 analogues with modifications in position 2 were not cleaved by DPP IV and showed receptor affinity and in vitro biological activity comparable to native GLP-1. Analogues with alterations in positions 2 and 8, 2 and 9 or 8 and 9 showed a significant decrease in receptor affinity and biological activity. In vivo biological activity was tested in pigs. GLP-1 analogues were administered subcutaneously followed by an intravenous bolus injection of glucose. Plasma glucose and insulin were monitored over 4 h. Compared to native GLP-1, analogues with an altered position 2 showed similar or increased potency and biological half-time. Other GLP-1 analogues were less active. Despite the lack of degradation of these GLP-1 analogues by DPP IV in vitro, their biological action is as short as that of GLP-1, except for desamino-GLP-1, indicating that other degradation enzymes are important in vivo. Alterations of GLP-1 in positions 8 or 9 result in a loss of biological activity without extending biological half-time.     

A cross-sectional survey among patients and prescribers on insulin dosing irregularities and impact of mild (self-treated) hypoglycemia episodes in Spanish patients with type 2 diabetes as compared to other European patients

Background and objectiveIn Spain, data suggest that 13.8% of adults have diabetes. Two important aspects in diabetes management are mild hypoglycemic episodes and poor treatment adherence. This study assesses the impact of missed insulin doses and prevalence of mistimed and reduced insulin doses and mild hypoglycemia in patients with type 2 diabetes treated with basal insulin analogues in Spain, and compares the data collected to pooled data from 8 other European countries (OECs).Materials and methodsGAPP2 was an international, online, cross-sectional study of diabetic patients aged ≥40 years treated with long-acting insulin analogues and their healthcare professionals. Patients and healthcare professionals were recruited from online research panels. Data reported in Spain are compared to pooled data from 8 OECs.ResultsIn Spain, 1–3% of patients reported they had reduced, missed, or mistimed at least one insulin does in the previous month. Significantly more OEC patients reported dosing irregularities (15–23%; all P < 0.01). In Spain, 77% of patients were worried and 59% felt guilty for missing a dose of basal insulin, while 24% reported that they were very worried about nocturnal hypoglycemia. Significantly fewer OEC patients reported worrying (47%; P < 0.01) and feeling guilty (37%; P < 0.01) about missing an insulin dose, or worry about nocturnal hypoglycemia (12%; P < 0.01).ConclusionsIn Spain, patients with type 2 diabetes report fewer dosing irregularities and hypoglycemic episodes as compared to patients from OECs. However, Spanish patients appear to have a reduced quality of life related to hypoglycemia as well as worry and guilt related to insulin dosing irregularities.     

Enhanced protection against cytokine- and fatty acid-induced apoptosis in pancreatic beta cells by combined treatment with glucagon-like peptide-1 receptor agonists and insulin analogues.

We recently showed that insulin analogues exhibit a beta-cell protective function. The aim of this study was to test if the anti-apoptotic activity of GLP-1 agonists and insulin analogues is mediated by different pathways and if combined treatment may provide augmented protection against beta-cell death. Incubation of INS-1 cells with cytokines or fatty acids increased the number of apoptotic cells and caspase 3 activity, which was reduced by pretreatment with GLP-1 and its receptor agonists exendin-4 and AVE0010 by 50-60%. Similar effects (about 40% reduction) were observed after pretreatment with several insulin analogues. Combined treatment revealed additive activity and resulted in prevention of both cytokine- and fatty acid-induced apoptosis by up to 80%. No acute Akt-phosphorylation in response to GLP-1 receptor agonists could be observed, however, it became detectable after 24-hour stimulation. Gene silencing of Akt2 increased cytokine-induced apoptosis 2-fold. Under these conditions the beta-cell protective activity of AVE0010 remained completely unaltered. We show here that the anti-apoptotic activity of GLP-1 and its receptor agonists AVE0010 and exendin-4 is enhanced by addition of insulin analogues and that the anti-apoptotic action of GLP-1 mimetics is mostly unrelated to Akt2 signaling. It is suggested that combination of GLP-1 receptor agonists and insulin analogues, specifically insulin glargine, may represent a new therapeutic option for preservation of beta-cell mass in type 2 diabetic patients.     

The Use of Premixed Insulin Analogues in the Treatment of Patients with Type 2 Diabetes Mellitus: Advantages and Limitations

Background:Intensive, target-oriented therapy is the standard of care in the management of patients with type 2 diabetesmellitus (DM). Early and aggressive use of insulin that is as close as possible to the physiologic pattern of insulin secretion from healthy pancreatic β-cells is advocated to achieve glycemic goals and reduce complications of DM.Objective:The objective of this article was to review the characteristics, advantages, and drawbacks of premixedinsulin analogues and to evaluate their role in the treatment of patients with type 2 DM.Methods:A PubMed search of articles from 1990 to 2006 was undertaken using the search terms type 2 diabetes, basalbolus therapy, premixed insulins, biphasic insulins, and insulin analogues. Pertinent content from relevant articles was extracted and combined with the authors' knowledge, experience, and clinical expertise.Results:The advent of insulin analogues has streamlined the treatment of patients with DM. When to initiate insulin during the course of treatment is the subject of much debate. Insulin therapy targeting both fasting and postprandial hyperglycemia is important in achieving optimal blood glucose (BG) control in patients with type 2 DM. A practical and feasible option is the use of >1 injection of premixed insulin analogues. Premixed insulin preparations provide both basal and prandial coverage because of their biphasic pharmacokinetic properties. Clinical trials have shown that these agents improve glycemic control, are associated with an acceptably low rate of severe hypoglycemia, and have a high degree of patient acceptance. Limitations include the inability to adjust the long- and short-acting components separately, to use a flexible regimen of self-titration and premeal bolus-insulin calculations, and to adequately treat postlunch and earlymorning BG elevations.Conclusion:Clinicians should be aware of premixed insulin analogues' advantages and limitations so that these agentscan be used appropriately in the treatment of patients with type 2 DM.     

Regulation of insulin and glucagon secretion from rat pancreatic islets in vitro by somatostatin analogues

Somatostatin is an inhibitor of hormone secretion through specific receptors (sst1-5). The aim of this study was to investigate the putative regulatory role of somatostatin analogues on the secretion of insulin and glucagon by rat pancreatic islets. After 48 h exposure only the non-selective agonists (somatostatin, octreotide and SOM-230) inhibited insulin accumulation. The inhibition of insulin secretion was accompanied by increased islet insulin contents. None of the analogues showed a consistent effect on the glucagon accumulation in the medium after 48 h. Since we observed a difference in the regulatory effect between the non-selective and selective analogues, combinations of selective analogues were studied. Combination of sst2+sst5 agonists inhibited the medium insulin accumulation, while combination of sst1+sst2 analogues caused a decrease in glucagon accumulation. After removal of somatostatin a rebound effect with increased insulin secretion were observed. This effect was reversed after 6 h. For SOM-230 insulin secretion continued to be suppressed even after the analogue was removed and returned to control values after 3 h. As for glucagon secretion there was an initial decline after culture with octreotide, while the other substances failed to induce any changes. In summary, non-selective somatostatin analogues or combinations of receptor selective analogues may cause inhibition of hormone secretion from rat pancreatic islets. For insulin and glucagon, combinations of sst2+sst5 and sst1+sst2, respectively may exert this effects. Thus, our data suggest that more than one sst must be involved to down-regulate islet glucagon and insulin secretion.     

Insulin analogues with modifications at position B26. Divergence of binding affinity and biological activity

In this study, we prepared several shortened and full-length insulin analogues with substitutions at position B26. We compared the binding affinities of the analogues for rat adipose membranes with their ability to lower the plasma glucose level in nondiabetic Wistar rats in vivo after subcutaneous administration, and also with their ability to stimulate lipogenesis in vitro. We found that [NMeHisB26]-DTI-NH 2 and [NMeAlaB26]-DTI-NH 2 were very potent insulin analogues with respect to their binding affinities (214 and 465%, respectively, compared to that of human insulin), but they were significantly less potent than human insulin in vivo. Their full-length counterparts, [NMeHisB26]-insulin and [NMeAlaB26]-insulin, were less effective than human insulin with respect to binding affinity (10 and 21%, respectively) and in vivo activity, while [HisB26]-insulin exhibited properties similar to those of human insulin in all of the tests we carried out. The ability of selected analogues to stimulate lipogenesis in adipocytes was correlated with their biological potency in vivo. Taken together, our data suggest that the B26 residue and residues B26-B30 have ambiguous roles in binding affinity and in vivo activity. We hypothesize that our shortened analogues, [NMeHisB26]-DTI-NH 2 and [NMeAlaB26]-DTI-NH 2, have different modes of interaction with the insulin receptor compared with natural insulin and that these different modes of interaction result in a less effective metabolic response of the insulin receptor, despite the high binding potency of these analogues.     

Incretin hormones in the treatment of type 2 diabetes. Part II. Incretins - new possibilities for pharmacotherapy of type 2 diabetes

In the pathogenesis of diabetes type 2, increasing insulin resistance is accompanied by dysfunction of pancreatic islet b cells. It is hypothesized that at the basis of this pathology lies an incretin defect of insulinotropic gut-derived hormones, relying on decreased secretion of GLP-1 (glucagon-like peptide 1), with preserved insulinotropic effect, whereas GIP (glucose-dependent insulinotropic polypeptide) secretion remains within physiological limits, but its action is mostly impaired due to total loss of possibility for stimulation of the second phase insulin secretion. Possibilities for pharmacological correction of incretin defect create an opportunity of causative treatment of diabetes and provide basis for development of research on a new group of drugs which promote hypoglycemia. In the presence of these findings there are many ongoing clinical studies with the use of GLP-1 analogues or GLP-1 receptors activators (GLP-1 agonists), as well as the inhibitors of dipeptidyl peptidase IV (DPP-IV), the enzyme responsible for incretin proteolysis, in the treatment of type 2 diabetes. Multidirectional, glucoregulative mechanism of action of these drugs, aiming at the pathogenesis of the disease, restores the proper function of the intestinal-pancreatic axis in subjects with type 2 diabetes and ensures good metabolic control and improvement in quality of life in this group of patients.     

Novel use of fluorescent glucose analogues to identify a new class of triazine-based insulin mimetics possessing useful secondary effects

There is an urgent need to discover new compounds that effectively treat diabetes by mimicking the action of insulin (insulin mimetics). Traditional approaches to studying anti-diabetic agents in cells are inconvenient for screening chemical libraries to identify insulin mimetics. 2-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG) and 6-NBDG are fluorescent analogues of glucose that could be employed in screening. However, there are no published data about the use of these analogues to identify new insulin mimetics. We have developed a screening system based on 6-NBDG using 3T3-L1 adipocytes in a 96-well culture plate format. 6-NBDG was found to produce a larger signal than 2-NBDG in this screening system. 6-NBDG uptake in 3T3-L1 adipocytes was sensitive to insulin, known insulin mimetics, inhibitors of glucose transport and insulin-sensitizing compounds. To validate our screening system, a chemical library of 576 tagged, triazine-based small molecules was screened. The screening results were identical to that obtained from a commercial enzyme-based glucose assay. Two inducers of glucose uptake were shown to be non-cytotoxic and confirmed as insulin mimetic compounds by their inhibition of epinephrine-stimulated free fatty acid release from adipocytes. These novel insulin mimetics functioned at a markedly lower concentration than two widely studied insulin mimetics, zinc(ii) complexes and vanadium compounds, and also showed novel, beneficial effects on endothelial cell function (a key determinant of secondary complications in diabetes). The discovery of new insulin mimetics using 6-NBDG validates the use of this probe in the development of large-scale, cell-based screening systems based on the uptake of fluorescent-tagged glucose analogues. This research should aid the development of novel strategies to discover new drugs and drug targets for combating the increasing prevalence of diabetes.     

Systematic evaluation of the metabolic to mitogenic potency ratio for B10-substituted insulin analogues

Background

Insulin analogues comprising acidic amino acid substitutions at position B10 have previously been shown to display increased mitogenic potencies compared to human insulin and the underlying molecular mechanisms have been subject to much scrutiny and debate. However, B10 is still an attractive position for amino acid substitutions given its important role in hexamer formation. The aim of this study was to investigate the relationships between the receptor binding properties as well as the metabolic and mitogenic potencies of a series of insulin analogues with different amino acid substitutions at position B10 and to identify a B10-substituted insulin analogue without an increased mitogenic to metabolic potency ratio.

Methodology/Principal Findings

A panel of ten singly-substituted B10 insulin analogues with different amino acid side chain characteristics were prepared and insulin receptor (both isoforms) and IGF-I receptor binding affinities using purified receptors, insulin receptor dissociation rates using BHK cells over-expressing the human insulin receptor, metabolic potencies by lipogenesis in isolated rat adipocytes, and mitogenic potencies using two different cell types predominantly expressing either the insulin or the IGF-I receptor were systematically investigated. Only analogues B10D and B10E with significantly increased insulin and IGF-I receptor affinities as well as decreased insulin receptor dissociation rates displayed enhanced mitogenic potencies in both cell types employed. For the remaining analogues with less pronounced changes in receptor affinities and insulin receptor dissociation rates, no apparent correlation between insulin receptor occupancy time and mitogenicity was observed.

Conclusions/Significance

Several B10-substituted insulin analogues devoid of disproportionate increases in mitogenic compared to metabolic potencies were identified. In the present study, receptor binding affinity rather than insulin receptor off-rate appears to be the major determinant of both metabolic and mitogenic potency. Our results also suggest that the increased mitogenic potency is attributable to both insulin and IGF-I receptor activation.     

Actual treatment with insulin in children and adolescents with diabetes type 1

A significant progress in the therapy of type 1 diabetes has been achieved. This was mainly because glucometers are now introduced in the majority of patients, better pens for insulin injections are now available. A progress was done in the methods of education and insulin analogues like Humalog were introduced. Therefore it is now possible to achieve a better metabolic compensation because of a more physiologic insulin action. A further progress is the introduction of long acting analogues and personal insulin pumps for the therapy. There are a lot of examinations about the epidemiology and prophylaxis of diabetes.     

Importance of aliphatic side-chain structure at positions 2 and 3 of the insulin A chain in insulin-receptor interactions.

In order to evaluate the cause of the greatly decreased receptor-binding potency of the naturally occurring mutant human insulin Insulin Wakayama ([LeuA3]insulin, 0.2% relative potency), we examined (by the semisynthesis of insulin analogues based on N alpha-PheB1,N epsilon-LysB29-bisacetyl-insulin) the importance of aliphatic side chain structure at positions A2 and A3 (Ile and Val, respectively) in directing the interaction of insulin with its receptor. Analogues bearing glycine, alanine, alpha-amino-n-butyric acid, norvaline, norleucine, valine, isoleucine, allo-isoleucine, threonine, tert-leucine, or leucine at positions A2 or A3 were assayed for their potencies in competing for the binding of 125I-labeled insulin to isolated canine hepatocytes, as were analogues bearing deletions from the A-chain amino terminus or the B-chain carboxyl terminus. Selected analogues were also analyzed by far-UV CD and absorption spectroscopy of Co2+ complexes. Our results identify that (a) Ile and Val serve well at position A2, whereas residues with other side chains (including those with straight chains, alternatively configured beta-branches, or a gamma-branch) exhibit relative receptor-binding potencies in the range 1-5%; (b) greater flexibility is allowed side-chain structure at position A3, with Ile, allo-Ile, alpha-amino-n-butyric acid, and tert-Leu exhibiting relative receptor-binding potencies in the range 11-36%; and (c) simultaneous replacements at positions A2 and A3, and deletions of the COOH-terminal domain of the insulin B chain in related analogues, yield cumulative effects. These findings are discussed with respect to a model for insulin-receptor interactions that involves a structure-orienting role for residue A2, the direct interaction of residue A3 with receptor, and multiple separately defined elements of structure and of conformational adjustment.