Effects of 4 weeks' administration of pramlintide, a human amylin analogue, on glycaemia control in patients with IDDM: effects on plasma glucose profiles and serum fructosamine concentrations

Mediators of Amylin Action in Metabolic Control

Amylin (also called islet amyloid polypeptide (IAPP)) is a pancreatic beta-cell hormone that is co-secreted with insulin in response to nutrient stimuli. The last 35 years of intensive research have shown that amylin exerts important physiological effects on metabolic control. Most importantly, amylin is a physiological control of meal-ending satiation, and it limits the rate of gastric emptying and reduces the secretion of pancreatic glucagon, in particular in postprandial states. The physiological effects of amylin and its analogs are mediated by direct brain activation, with the caudal hindbrain playing the most prominent role. The clarification of the structure of amylin receptors, consisting of the calcitonin core receptor plus receptor-activity modifying proteins, aided in the development of amylin analogs with a broad pharmacological profile. The general interest in amylin physiology and pharmacology was boosted by the finding that amylin is a sensitizer to the catabolic actions of leptin. Today, amylin derived analogs are considered to be among the most promising approaches for the pharmacotherapy against obesity. At least in conjunction with insulin, amylin analogs are also considered important treatment options in diabetic patients, so that new drugs may soon be added to the only currently approved compound pramlintide (Symlin^®). This review provides a brief summary of the physiology of amylin’s mode of actions and its role in the control of the metabolism, in particular energy intake and glucose metabolism.

Dual-hormone artificial pancreas for management of type 1 diabetes: Recent progress and future directions

Over the last few years, technological advances have led to tremendous improvement in the management of type 1 diabetes (T1D). Artificial pancreas systems have been shown to improve glucose control compared with conventional insulin pump therapy. However, clinically significant hypoglycemic and hyperglycemic episodes still occur with the artificial pancreas. Postprandial glucose excursions and exercise-induced hypoglycemia represent major hurdles in improving glucose control and glucose variability in many patients with T1D. In this regard, dual-hormone artificial pancreas systems delivering other hormones in addition to insulin (glucagon or amylin) may better reproduce the physiology of the endocrine pancreas and have been suggested as an alternative tool to overcome these limitations in clinical practice. In addition, novel ultra-rapid-acting insulin analogs with a more physiological time-action profile are currently under investigation for use in artificial pancreas devices, aiming to address the unmet need for further improvements in postprandial glucose control. This review article aims to discuss the current progress and future outlook in the development of novel ultra-rapid insulin analogs and dual-hormone closed-loop systems, which offer the next steps to fully closing the loop in the artificial pancreas.

Efficacy and safety of pramlintide injection adjunct to insulin therapy in patients with type 1 diabetes mellitus: a systematic review and meta-analysis

AIMS

We aim to assess the efficacy and safety of pramlintide plus insulin therapy in patients with type 1 diabetes.

METHODS

We included clinical studies comparing pramlintide plus insulin to placebo plus insulin. Efficacy was reflected by glycemic control and reduction in body weight and insulin use. Safety concerns were hypoglycemia and other adverse events. Subgroup analysis was performed for different doses (30, 60, 90 µg/meal) and durations (≤4, 26, 29, >29 weeks) of the treatment.

RESULTS

A total of 10 randomized placebo-controlled studies were included for this meta-analysis (pramlintide, n=1978; placebo, n=1319). Compared with controls, patients given pramlintide had significantly lower HbA1c (p < 0.001), total daily insulin dose (p = 0.024), mean mealtime insulin dose (p < 0.001), body weight (p < 0.001) and postprandial glucose level (p = 0.002). The addition of pramlintide increased the incidence of nausea (p < 0.001), vomiting (p < 0.001), anorexia (p < 0.001) and hypoglycemia (p < 0.05) at the initiation of the treatment. The efficacy and adverse reactions of pramlintide were largely significant for the different doses and durations of the treatment.

CONCLUSIONS

The addition of pramlintide to insulin therapy in patients with type 1 diabetes improves glycemic control and reduces insulin requirement and body weight while bringing transient hypoglycemia and digestive disorders.

Rationale for treatment options for mealtime glucose control in patients with type 2 diabetes

While glycemic control is routinely assessed using HbA1c and fasting glucose measures, postprandial glucose (PPG) is also an important contributor of overall glycemia. Furthermore, PPG excursions have been linked to complications of diabetes. This review examines the effects of glucose-lowering therapies (including treatments administered at mealtime) on postprandial hyperglycemia in patients with type 2 diabetes. A PubMed search was conducted to identify clinical studies of treatments for mealtime glucose control in type 2 diabetes. Different treatments may have comparable effects on HbA1c but varying effects on PPG control and glucose fluctuations. Older classes of oral glucose-lowering treatments administered at mealtime to lower PPG include meglitinides and α-glucosidase inhibitors. Injectable therapies, including prandial insulin analogs, glucagon-like peptide-1 receptor agonists (GLP-1RAs), and the amylin analog pramlintide, all effectively target postprandial hyperglycemia. Compared with longer-acting GLP-1RAs, short-acting GLP-1RAs, such as exenatide twice daily and lixisenatide once daily, have a greater effect on PPG control, which is primarily mediated by a more pronounced effect on delayed gastric emptying. Dipeptidyl peptidase-4 inhibitors and sodium-glucose cotransporter 2 inhibitors also reduce postprandial hyperglycemia. To achieve more physiologically normal glycemic control, choice of therapy should ideally aim to address daily glucose fluctuations, including hyperglycemic peaks and hypoglycemic troughs, and long-term glycemic control.

A model of glucose-insulin-pramlintide pharmacokinetics and pharmacodynamics in type I diabetes

Type 1 diabetes mellitus (T1DM) complications are significantly reduced when normoglycemic levels are maintained via intensive therapy. The artificial pancreas is designed for intensive glycemic control; however, large postprandial excursions after a meal result in poor glucose regulation. Pramlintide, a synthetic analog of the hormone amylin, reduces the severity of postprandial excursions by reducing appetite, suppressing glucagon release, and slowing the rate of gastric emptying. The goal of this study is to create a glucose-insulin-pramlintide physiological model that can be employed into a controller to improve current control approaches used in the artificial pancreas. A model of subcutaneous (SC) pramlintide pharmacokinetics (PK) was developed by revising an intravenous (IV) pramlintide PK model and adapting SC insulin PK from a glucose-insulin model. Gray-box modeling and least squares optimization were used to obtain parameter estimates. Pharmacodynamics (PD) were obtained by choosing parameters most applicable to pramlintide mechanisms and then testing using a proportional PD effect using least squares optimization. The model was fit and validated using 27 data sets, which included placebo, PK, and PD data. SC pramlintide PK root mean square error values range from 1.98 to 10.66 pmol/L. Pramlintide PD RMSE values range from 10.48 to 42.76 mg/dL. A new in silico model of the glucose-insulin-pramlintide regulatory system is presented. This model can be used as a platform to optimize dosing of both pramlintide and insulin as a combined therapy for glycemic regulation, and in the development of an artificial pancreas as the kernel for a model-based controller.

Amylin uncovered: a review on the polypeptide responsible for type II diabetes

Amylin is primarily responsible for classifying type II diabetes as an amyloid (protein misfolding) disease as it has great potential to aggregate into toxic nanoparticles, thereby resulting in loss of pancreatic β-cells. Although type II diabetes is on the increase each year, possibly due to bad eating habits of modern society, research on the culprit for this disease is still in its early days. In addition, unlike the culprit for Alzheimer's disease, amyloid β-peptide, amylin has failed to receive attention worthy of being featured in an abundance of review articles. Thus, the aim of this paper is to shine the spotlight on amylin in an attempt to put it onto the top of researchers' to-do list since the secondary complications of type II diabetes have far-reaching and severe consequences on public health both in developing and fully developed countries alike. This paper will cover characteristics of the amylin aggregates, mechanisms of toxicity, and a particular focus on inhibitors of toxicity and techniques used to assess these inhibitors.

Insulin secretion in healthy subjects and patients with Type 2 diabetes--role of the gastrointestinal tract

Postprandial glycaemia is now recognised as the major determinant of average glycaemic control in type 2 diabetes, as assessed by glycated haemoglobin. Therefore, an understanding of the factors influencing both the rise in blood glucose and insulin secretion after a meal is fundamental to the development of dietary and pharmacological approaches to optimise glycaemic control. The gastrointestinal tract regulates the rate at which carbohydrate and other nutrients are absorbed and is the source of regulatory peptides that stimulate pancreatic insulin secretion in the setting of elevated blood glucose levels. This article highlights the importance of the gastrointestinal tract in insulin secretion and glucose homeostasis and discusses potential strategies directed at modification of gastrointestinal function in order to improve glycaemic control in the management of diabetes.

Review of pramlintide as adjunctive therapy in treatment of type 1 and type 2 diabetes

Pramlintide (Symlin^®), a synthetic analog of a neurohormone amylin, was approved by the US Food and Drug Administration for use along with premeal insulin in patients with type 1. In patients with type 2 diabetes, pramlintide is approved for addition to premeal insulin in those patients who are either only on premeal insulin or those receiving the combination of insulin and metformin and/or a sulfonylurea. This article reviews the pharmacology, pharmacokinetics, dosing, clinical trials, safety, contraindications, and drug interactions of pramlintide therapy. A search for published clinical trials and therapeutic reviews in the English language was done in the following databases: Iowa Drug Information Service (1966 to July 2008), MEDLINE (1966 to July 2008), and International Pharmaceutical Abstracts (1970 to July 2008). Pramlintide and amylin were used as keywords and title words. References of key articles were also reviewed to identify additional publications. Amylin is a 37 amino acid peptide neurohormone cosecreted from the beta cells of the pancreas, along with insulin, in response to meals. Amylin lowers serum glucose by decreasing glucagon release, slowing gastric emptying and decreasing food intake. Pramlintide, a synthetic analog of amylin, reduces 2-hour postprandial blood glucose between 3.4 and 5 mmol/L, reduces A1C by 0.2% to 0.7% and has no effect on fasting glucose levels. The use of pramlintide was associated with up to a 1.6 kg weight loss. Nausea was the most commonly reported adverse event. Pramlintide is an amylin analog that was FDA approved for the treatment of type 1 and type 2 diabetes. Its use results in modest reduction of A1C and the most frequent side effects are hypoglycemia and nausea.

Pramlintide, the synthetic analogue of amylin: physiology, pathophysiology, and effects on glycemic control, body weight, and selected biomarkers of vascular risk

Pramlintide is a synthetic version of the naturally occurring pancreatic peptide called amylin. Amylin and pramlintide have similar effects on lowering postprandial glucose, lowering postprandial glucagon and delaying gastric emptying. Pramlintide use in type 1 and insulin requiring type 2 diabetes mellitus (DM) is associated with modest reductions in HbA1c often accompanied by weight loss. Limited data show a neutral effect on blood pressure. Small studies suggest small reductions in LDL-cholesterol in type 2 DM and modest reductions in triglycerides in type 1 DM. Markers of oxidation are also reduced in conjunction with reductions in postprandial glucose. Nausea is the most common side effect. These data indicate that pramlintide has a role in glycemic control of both type 1 and type 2 DM. Pramlintide use is associated with favorable effects on weight, lipids and other biomarkers for atherosclerotic disease.

Upper gastrointestinal function and glycemic control in diabetes mellitus

Recent evidence has highlighted the impact of glycemic control on the incidence and progression of diabetic micro- and macrovascular complications, and on cardiovascular risk in the non-diabetic population. Postprandial blood glucose concentrations make a major contribution to overall glycemic control, and are determined in part by upper gastrointestinal function. Conversely, poor glycemic control has an acute, reversible effect on gastrointestinal motility. Insights into the mechanisms by which the gut contributes to glycemia have given rise to a number of novel dietary and pharmacological strategies designed to lower postprandial blood glucose concentrations.

Newer therapeutic options for children with diabetes mellitus: theoretical and practical considerations

Recent studies in adult patients with type 1 diabetes mellitus (T1DM) and T2DM have examined the potential utility, benefits, and side effects of agents that augment insulin secretion after oral ingestion of nutrients in comparison with intravenous nutrient delivery, the so-called incretins. Two families of incretin-like substances are now approved for use in adults. Glucagon-like peptide-1 (GLP-1) or agents that bind to its receptor (exenatide, Byetta) or agents that inhibit its destruction [dipeptidyl peptidase-IV (DPP-IV) inhibitors, Vildagliptin] improve insulin secretion, delay gastric emptying, and suppress glucagon secretion while decreasing food intake without increasing hypoglycemia. Pramlintide, a synthetic amylin analog, also decreases glucagon secretion and delays gastric emptying, improves hemoglobin A1c (HbA1C), and facilitates weight reduction without causing hypoglycemia. We review the historical discovery of these agents, their physiology [corrected] and their current applications. Remarkably, only one or two studies have been reported in children. Pediatricians caring for children with T1DM and T2DM should become familiar with these agents and investigate their applicability, as they seem likely to enhance our therapeutic armamentarium to treat children with diabetes mellitus.

Pramlintide in the treatment of type 1 and type 2 diabetes mellitus

BACKGROUND

Amylin is a 37-amino acid peptide neurohormone that is cosecreted with insulin from the pancreatic beta cells in response to meals. It lowers serum glucose by decreasing glucagon release, slowing gastric emptying, and decreasing food intake. Pramlintide, a synthetic amylin analogue, is approved by the US Food and Drug Administration for use with mealtime insulin in patients with type 1 diabetes and patients with type 2 diabetes who are using mealtime insulin only or the combination of insulin and metformin and/or a sulfonylurea.

OBJECTIVE

This article reviews the available literature on pramlintide with respect to its mechanism of action, pharmacokinetics and pharmacodynamics, clinical efficacy in type 1 and type 2 diabetes, safety and tolerability, dosing, contraindications, and drug interactions.

METHODS

MEDLINE (1966-April 2005), Iowa Drug Information Service (1966-April 2005), and International Pharmaceutical Abstracts (1970-April 2005) were searched for clinical trials and therapeutic reviews published in the English language. The search terms were pramlintide and amylin. The bibliographies of identified articles were reviewed for additional references. All relevant studies were included in the review.

RESULTS

Six studies, ranging in duration from 4 to 52 weeks, examined the effect of administering pramlintide with premeal insulin in patients with type 1 diabetes. In these trials, pramlintide 120 to 270 microg/d reduced glycosylated hemoglobin (HbA(1c)) by 0.1 % to 0.67%, 1-hour postprandial glucose (PPG) by 4.4 to 7 mmol/L, and 2-hour PPG by 3.6 to 4.8 mmol/L. Five studies, also ranging from 4 to 52 weeks' duration, examined the effect of administering premeal pramlintide in patients with type 2 diabetes. In these trials, pramlintide 90 to 450 microg/d reduced HbA(1c) by 0.3% to 0.62%, 1-hour PPG by 4.8 mmol/L, and 2-hour PPG by 3.4 mmol/L. The principal adverse events reported in clinical trials were nausea and hypoglycemia. The incidence of hypoglycemia in the first 4 weeks of therapy was 2 to 4 times greater with pramlintide compared with placebo; thus, the manufacturer recommends reducing the dose of premeal insulin by 50% when starting pramlintide. Close monitoring of blood glucose levels is recommended when initiating pramlintide therapy.

CONCLUSIONS

Use of pramlintide in addition to insulin in patients with type 1 and type 2 diabetes was associated with modest reductions in HbA(1c). The primary adverse effects of pramlintide therapy were nausea and hypoglycemia.

Pramlintide acetate

PURPOSE

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage and administration of pramlintide are reviewed.

SUMMARY

Pramlintide, a synthetic analogue of the human hormone amylin, is the first of a new class of amylinomimetic compounds. It was approved in March 2005 as a subcutaneous injection for the adjunctive treatment of patients who have type 1 or 2 diabetes mellitus and have failed to achieve glycemic control despite optimal therapy with insulin. Pramlintide complements the effects of insulin in postprandial glucose regulation by decreasing glucagon secretion. Pramlintide exhibits linear pharmacokinetics, and peak serum levels are reached within 30 minutes of administration. The drug is predominantly renally eliminated, with a mean elimination half-life of 30-50 minutes. Clinical trials have shown that pramlintide suppresses postmeal glucagon secretion, slows gastric emptying, reduces postprandial glucose levels, and improves glycemic control while managing weight loss. Pramlintide has also been shown to decrease hemoglobin A(1c), serum fructosamine, and total cholesterol levels. Pramlintide has been associated with an increased risk of insulin-induced severe hypoglycemia; other adverse events include nausea, anorexia, fatigue, and vomiting. The dosage varies with the type of diabetes. Because of the cost associated with the complications of uncontrolled diabetes, pramlintide may have a beneficial effect on total costs associated with this chronic disease.

CONCLUSION

Pramlintide in combination with insulin is a potential therapeutic option for improving glycemic control in patients with diabetes, but the increased risk of hypoglycemia must be aggressively monitored.

Properties of pramlintide and insulin upon mixing

PURPOSE

The pharmacokinetics, pharmacodynamics, and safety of pramlintide and various insulin formulations in patients with type 1 diabetes mellitus (DM) when given as separate injections or mixed in the same syringe before injection were studied.

METHODS

In two randomized, open-label, placebo-controlled, five-period-crossover studies, patients with type 1 DM received preprandial injections of pramlintide, short-acting insulin, and long-acting insulin administered either by separate injections or after mixing in various combinations. Serum free insulin and plasma glucose concentrations were measured for 10 hours and plasma pramlintide concentrations for 5 hours after injection.

RESULTS

Blood samples were collected from a total of 51 patients. All treatments involving mixtures were comparable to separate injections with respect to the area under the concentration-versus-time curve (AUC) and the maximum concentration (Cmax) of serum free insulin. There were some minor differences in the AUC and Cmax of pramlintide. No injection-site reactions or other unexpected adverse events were observed.

CONCLUSION

Mixing pramlintide with short- or long-acting insulin in the same syringe before subcutaneous injection did not affect the pharmacodynamics of glucose or the pharmacokinetics of insulin or pramlintide in a clinically significant manner.

Pramlintide Acetate

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Clinical studies

Recognizing that type 1 diabetes was characterized not only by insulin deficiency, but also by amylin deficiency, Cooper (Cooper, 1991) predicted that certain features of the disease could be related thereto, and he proposed amylin/insulin co-replacement therapy. Although the early physiological rationale was flawed, the idea that glucose control could be improved over that attainable with insulin alone without invoking the ravages of worsening insulin-induced hypoglycemia was vindicated. The proposal spawned a first-in-class drug development program that ultimately led to marketing approval by the U.S. Food and Drug Administration of the amylinomimetic pramlintide acetate in March 2005. The prescribers' package insert (Amylin Pharmaceuticals Inc., 2005), which includes a synopsis of safety and efficacy of pramlintide, is included as Appendix 1. Pramlintide exhibited a terminal t1/2, in humans of 25-49 min and, like amylin, was cleared mainly by the kidney. The dose-limiting side effect was nausea and, at some doses, vomiting. These side effects usually subsided within the first days to weeks of administration. The principal risk of pramlintide co-therapy was an increased probability of insulin-induced hypoglycemia, especially at the initiation of therapy. This risk could be mitigated by pre-emptive reduction in insulin dose. Pramlintide dosed at 30-60 microg three to four times daily in patients with type 1 diabetes, and at doses of 120 microg twice daily in patients with type 2 diabetes, invoked a glycemic improvement, typically a decrease in HbA1c of 0.4-0.5% relative to placebo, that was sustained for at least 1 year. This change relative to control subjects treated with insulin alone typically was associated with a reduction in body weight and insulin use, and was not associated with an increase in rate of severe hypoglycemia other than at the initiation of therapy. Effects observed in animals, such as slowing of gastric emptying, inhibition of nutrient-stimulated glucagon secretion, and inhibition of food intake, generally have been replicated in humans. A notable exception appears to be induction of muscle glycogenolysis and increase in plasma lactate.

Amylin agonists: a novel approach in the treatment of diabetes

Amylin is a peptide hormone that is cosecreted with insulin from the pancreatic beta-cell and is thus deficient in diabetic people. It inhibits glucagon secretion, delays gastric emptying, and acts as a satiety agent. Amylin replacement could therefore possibly improve glycemic control in some people with diabetes. However, human amylin exhibits physicochemical properties predisposing the peptide hormone to aggregate and form amyloid fibers, which may play a part in beta-cell destruction in type 2 diabetes. This obviously makes it unsuitable for pharmacological use. A stable analog, pramlintide, which has actions and pharmacokinetic and pharmacodynamic properties similar to the native peptide, has been developed. The efficacy and safety of pramlintide administration has been tested in a vast number of clinical trials. Approximately 5,000 insulin-treated patients have received pramlintide and approximately 250 for > or =2 years. The aims of this review are to 1) briefly describe actions of amylin as demonstrated in animal and human models and 2) primarily review results from clinical trials with the amylin analog pramlintide.

Amylin replacement with pramlintide as an adjunct to insulin therapy improves long-term glycaemic and weight control in Type 1 diabetes mellitus: a 1-year, randomized controlled trial

AIMS

The autoimmune-mediated destruction of pancreatic beta-cells in Type 1 diabetes mellitus renders patients deficient in two glucoregulatory peptide hormones, insulin and amylin. With insulin replacement alone, most patients do not achieve glycaemic goals. We aimed to determine the long-term efficacy and safety of adjunctive therapy with pramlintide, a synthetic human amylin analogue, in patients with Type 1 diabetes.

METHODS

In a double-blind, placebo-controlled, parallel-group, multicentre study, 651 patients with Type 1 diabetes (age 41 +/- 13 years, HbA(1c) 8.9 +/- 1.0%, mean +/- sd) were randomized to mealtime injections of placebo or varying doses of pramlintide, in addition to their insulin therapy, for 52 weeks.

RESULTS

Addition of pramlintide [60 microg three times daily (TID) or four times daily (QID)] to insulin led to significant reductions in HbA(1c) from baseline to Week 52 of 0.29% (P < 0.011) and 0.34% (P < 0.001), respectively, compared with a 0.04% reduction in placebo group. Three times the proportion of pramlintide- than placebo-treated patients achieved an HbA(1c) of < 7%. The greater reduction in HbA(1c) with pramlintide was achieved without an increase in concomitant insulin use and was accompanied by a significant reduction in body weight from baseline to Week 52 of 0.4 kg in the 60 microg TID (P < 0.027) or QID (P < 0.040) pramlintide treatment groups, compared with a 0.8-kg gain in body weight in the placebo group. The most common adverse event in pramlintide-treated patients was transient, mild-to-moderate nausea.

CONCLUSIONS

These results show that mealtime amylin replacement with pramlintide, as an adjunct to insulin therapy, improves long-term glycaemic and weight control in patients with Type 1 diabetes.

Pramlintide for the treatment of diabetes mellitus

OBJECTIVE

To provide an overview of the role of amylin, as well as that of pramlintide, a synthetic analog of amylin, in maintaining glucose homeostasis; and discuss the pharmacology, pharmacokinetics, efficacy, adverse effects, and role of pramlintide in the control of postprandial hyperglycemia.

DATA SOURCES

The data presented in this review were obtained from published literature, abstracts presented at scientific meetings, and information on file with the manufacturer. MEDLINE searches (1986-March 2003) using the search terms pramlintide and amylin were conducted to identify clinical trials and review articles. Additionally, the bibliographies of the identified articles were reviewed.

DATA SYNTHESIS

Clinical trials have demonstrated that amylin in combination with insulin controls postprandial glucose levels by decreasing food intake, slowing gastric emptying, and suppressing glucagon secretion. Clinical trials also showed significant decreases in mean plasma glucose levels and glycosylated hemoglobin, as well as the added benefits of weight loss and reduction in insulin doses. The most commonly reported adverse effects associated with pramlintide in clinical trials were gastrointestinal complaints and hypoglycemia, which occurred most frequently during initiation of therapy.

CONCLUSIONS

The administration of insulin alone often does not result in optimal metabolic control. The treatment of amylin deficiency, in addition to insulin deficiency, may be warranted in order to obtain glucose homeostasis. The role of pramlintide, an amylin analog, will become clearer as more clinical data become available.

Effects of pramlintide, an amylin analogue, on gastric emptying in type 1 and 2 diabetes mellitus

Pramlintide delays gastric emptying, possibly by a centrally mediated mechanism. Our aim was to determine whether the effects of pramlintide on gastric emptying differ in people with type 1 or type 2 diabetes who had no history of complications. Using a randomized, three-period, two-dose, crossover design, we studied the effects of 0, 30, or 60 microg t.i.d. pramlintide subcutaneously for 5 days each in six type 1 and six type 2 diabetic subjects. Gastric emptying of solids was measured by 13C-Spirulina breath test. Plasma pancreatic polypeptide (HPP) response to the test meal was also measured. Relative to placebo [t 50% 91 +/- 6 min (means +/- SEM)], pramlintide equally delayed gastric emptying following 30 or 60 microg t.i.d. (268 +/- 37 min, 329 +/- 49 min, respectively; P < 0.01]. Postprandial HPP levels were lower in response to 30 and 60 microg pramlintide compared to placebo. There were no significant differences in the effects on gastric emptying or HPP levels between type 1 and type 2 diabetic subjects. Pramlintide delays gastric emptying in diabetes unassociated with clinically detected complications. Further studies are needed in diabetic patients with impaired gastric motor function.

Amylin receptor agonists: a novel pharmacological approach in the management of insulin-treated diabetes mellitus

Amylin is a peptide hormone which is co-secreted with insulin from the pancreatic beta-cell. Type 1 diabetic individuals and some Type 2 diabetic individuals are characterised by amylin deficiency. Animal experiments have revealed several actions of amylin on intermediary metabolism, of these some have been demonstrated to be of potential physiological relevance in humans. In particular amylin appears to have important actions in controlling prandial glucose homeostasis. The peptide hormone inhibits postprandial glucagon secretion and delays gastric emptying thereby modifying postprandial hyperglycaemia in diabetic individuals which presumably adds to overall glycaemic control without a concomitant increase in the number of severe hypoglycaemic episodes. Moreover, amylin acts as a satiety agent. Amylin replacement may therefore improve glycaemic control in diabetes mellitus. However, human amylin exhibits physicochemical properties predisposing the peptide hormone to aggregate and form amyloid fibres, which makes it unsuitable for pharmacological use. A stable analogue, pramlintide, with actions and pharmacokinetic and pharmacodynamic properties similar to the native peptide has therefore been developed. The efficacy and safety of pramlintide administration to diabetic individuals have been tested in a large number of clinical trials. It is the aim of this review to describe possible (patho)physiological actions of amylin as demonstrated in animal and human models, to discuss the background for potential amylin (analogue) replacement in diabetes mellitus and to review results from clinical trials with the amylin receptor analogue pramlintide.

Relationships of upper gastrointestinal motor and sensory function with glycemic control

Acute changes in the blood glucose concentration have a major reversible effect on esophageal, gastric, intestinal, gallbladder, and anorectal motility in both healthy subjects and diabetic patients. For example, gastric emptying is slower during hyperglycemia than euglycemia and accelerated during hypoglycemia. Acute hyperglycemia also affects perceptions arising from the gastrointestinal tract and may accordingly, be important in the etiology of gastrointestinal symptoms in diabetes. Elevations in blood glucose that are within the normal postprandial range also affect gastrointestinal motor and sensory function. Upper gastrointestinal motor function is a critical determinant of postprandial blood glucose concentrations by influencing the absorption of ingested nutrients. Interventions that reduce postprandial hyperglycemia, by modulating the rate of gastric emptying, have the potential to become mainstream therapies in the treatment of diabetes.

Pramlintide, an amylin analog, selectively delays gastric emptying: potential role of vagal inhibition

The amylin analog pramlintide delays gastric emptying in type I diabetics. The effects of multiple doses of pramlintide and the mechanism of action in non-amylin-deficient humans are unknown. We investigated the effects of pramlintide on gastrointestinal and colonic transit and on the plasma pancreatic polypeptide response to the meal in a parallel-group dose-response study with subjects randomized to placebo, or 30 or 60 microg (tid, sc) of pramlintide. Pramlintide delayed gastric emptying [half-time (t(1/2)): 112 min (SE 8.7 min), 169 min (SE 12 min), or 177 min (SE 25 min) after placebo or 30- or 60-microg pramlintide treatment, respectively; P = 0.033]. Pramlintide did not significantly affect small bowel or colonic transit. Pancreatic polypeptide concentrations in the first postprandial hour were lower with pramlintide than with placebo (P<0.01 for drug effect). An inverse correlation was observed between mean pancreatic polypeptide concentrations in the first postprandial hour and gastric emptying t(1/2) [Spearman correlation coefficient (R(s)) = 0.48; P = 0.044]. Pramlintide at 30 and 60 microg delays gastric emptying in healthy humans without affecting small bowel or colonic transit. Vagal inhibition is a potential mechanism of the effects of pramlintide on gastric emptying.

Cisapride versus placebo for 8 weeks on glycemic control and gastric emptying in insulin-dependent diabetes: a double blind cross-over trial

In insulin-dependent diabetes mellitus, slow gastric emptying may make absorption unpredictable and foster glycemic instability. Cisapride accelerates emptying, but controlled long term studies are scarce, and effects on glycemic control unknown. We investigated, in patients with insulin-dependent diabetes mellitus and unstable glycemia, the effects of 10 mg cisapride 4 times daily for 8 weeks vs. placebo on glycemic control and gastric emptying under random, cross-over, double blind conditions. In 14 patients with delayed and 9 with nondelayed emptying, blood glucose variability over 28-week treatment periods separated by a 4-week wash-out and gastric emptying of a semisolid 1168-kJ meal immediately after the treatment periods were assessed. Cisapride did not affect glycemic control [SD of within-patient mean blood glucose, 4.2 mmol/L +/-0.1 (+/- SEM) vs. 4.0+/-0.1 mmol/L after placebo; hemoglobin A1c, 8.3+/-0.2% vs. 8.5+/-0.2%]. Emptying was faster after cisapride than after placebo in 8 of 14 patients with delayed vs. 7 of 9 with nondelayed emptying (P = NS) and in 11 of 15 without vs. 4 of 8 with cardiovascular autonomic neuropathy (P = NS). Autonomic neuropathy prevailed in 7 of 14 patients with delayed and 1 of 9 with nondelayed emptying. Blood glucose immediately before and during assessment of emptying was unrelated to the emptying rate, whereas blood glucose increases over fasting levels were greater with faster emptying (P<0.002). In conclusion, cisapride's effects were not different from those of placebo on glycemic control and gastric emptying, it did not differently affect patients with delayed vs. nondelayed emptying, and it slightly accelerated emptying (P = NS) in patients without, but not in those with, cardiovascular autonomic neuropathy. Blood glucose levels before and during assessment of emptying did not affect emptying, but the glucose rise over fasting levels was greater with faster emptying.

The amylin analog pramlintide improves glycemic control and reduces postprandial glucagon concentrations in patients with type 1 diabetes mellitus

To explore further the effects of the human amylin analog pramlintide on overall glycemic control and postprandial responses of circulating glucose, glucagon, and metabolic intermediates in type 1 diabetes mellitus, 14 male type 1 diabetic patients were examined in a double-blind, placebo-controlled, crossover study. Pramlintide (30 microg four times daily) or placebo were administered for 4 weeks, after which a daytime blood profile (8:30 AM to 4:30 PM) was performed. Serum fructosamine was decreased after pramlintide (314+/-14 micromol/L) compared with placebo (350+/-14 micromol/L, P = .008). On the profile day, the mean plasma glucose (8.3+/-0.7 v 10.2+/-0.8 mmol/L, P = .04) and postprandial concentrations (incremental areas under the curve [AUCs] from 0 to 120 minutes) were significantly decreased during pramlintide administration (P < .01 for both) despite comparable circulating insulin levels (359+/-41 v 340+/-35 pmol/L). Mean blood glycerol values were reduced (0.029+/-0.004 v 0.040+/-0.004 mmol/L, P = .01) and blood alanine levels were elevated (0.274+/-0.012 v 0.246+/-0.008 mmol/L, P = .03) after pramlintide versus placebo. Blood lactate concentrations did not differ during the two regimens. During pramlintide administration, the AUC (0 to 120 minutes) for plasma glucagon after breakfast was diminished (P = .02), and a similar trend was observed following lunch. In addition, peak plasma glucagon concentrations 60 minutes after breakfast (45.8+/-7.3 v 72.4+/-8.0 ng/L, P = .005) and lunch (47.6+/-9.0 v 60.9+/-8.2 ng/L, P = .02) were both decreased following pramlintide. These data indicate that pramlintide (30 microg four times daily) is capable of improving metabolic control in type 1 diabetics. This may relate, in part, to suppression of glucagon concentrations. Longer-term studies are required to ascertain whether these findings are sustained over time.

Clinical implications of amylin and amylin deficiency

PURPOSE

This paper presents an overview of the physiology of glycemic control and the mechanisms of amylin deficiency in people with diabetes. Benefits of replacement therapy with both pramlintide and insulin are discussed.

METHODS

The discovery of the pancreatic beta-cell hormone amylin, which is cosecreted with insulin in response to hyperglycemia, has prompted a reanalysis of the mechanisms underlying the control of glucose homeostasis. A review of the current literature on amylin and amylin deficiency provides the basis of this reanalysis, with a discussion of the clinical implications for people with diabetes.

RESULTS

Amylin appears to work with insulin to regulate plasma glucose concentrations in the bloodstream, suppressing the postprandial secretion of glucagon and restraining the rate of gastric emptying. People with diabetes have a deficiency in the secretion of amylin that parallels the deficiency in insulin secretion, resulting in an excessive inflow of glucose into the bloodstream during the postprandial period.

CONCLUSIONS

While insulin replacement therapy is a cornerstone of diabetes treatment, replacement of the function of both amylin and insulin may allow a more complete restoration of the normal physiology of glucose control.