Effect of 14 days' subcutaneous administration of the human amylin analogue, pramlintide (AC137), on an intravenous insulin challenge and response to a standard liquid meal in patients with IDDM

A model of subcutaneous pramlintide pharmacokinetics and its effect on gastric emptying: Proof-of-concept based on populational data

Pramlintide, an amylin analog, has been coming up as an agent in type 1 diabetes dual-hormone therapies (insulin/pramlintide). Since pramlintide slows down gastric emptying, it allows for easing glucose control and reducing the burden of meal announcements. Pre-clinical in silico evaluations are a key step in the development of any closed-loop strategy. However, mathematical models are needed, and pramlintide models in the literature are scarce. This work proposes a proof-of-concept pramlintide model, describing its subcutaneous pharmacokinetics (PK) and its effect on gastric emptying (PD). The model is validated with published populational (clinical) data. The model development is divided into three stages: intravenous PK, subcutaneous PK, and PD modeling. In each stage, a set of model structures are proposed, and their performance is assessed using the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC). In order to evaluate the modulation of the rate of gastric emptying, a literature meal model was used. The final pramlintide model comprises four compartments and a function that modulates gastric emptying depending on plasma pramlintide. Results show an appropriate fit for the data. Some aspects are left as open questions due to the lack of specific data (e.g., the influence of meal composition on the pramlintide effect). Moreover, further validation with individual data is necessary to propose a virtual cohort of patients.

Ultra-Fast Insulin-Pramlintide Co-Formulation for Improved Glucose Management in Diabetic Rats

Dual-hormone replacement therapy with insulin and amylin in patients with type 1 diabetes has the potential to improve glucose management. Unfortunately, currently available formulations require burdensome separate injections at mealtimes and have disparate pharmacokinetics that do not mimic endogenous co-secretion. Here, amphiphilic acrylamide copolymers are used to create a stable co-formulation of monomeric insulin and amylin analogues (lispro and pramlintide) with synchronous pharmacokinetics and ultra-rapid action. The co-formulation is stable for over 16 h under stressed aging conditions, whereas commercial insulin lispro (Humalog) aggregates in 8 h. The faster pharmacokinetics of monomeric insulin in this co-formulation result in increased insulin-pramlintide overlap of 75 ± 6% compared to only 47 ± 7% for separate injections. The co-formulation results in similar delay in gastric emptying compared to pramlintide delivered separately. In a glucose challenge, in rats, the co-formulation reduces deviation from baseline glucose compared to insulin only, or separate insulin and pramlintide administrations. Further, comparison of interspecies pharmacokinetics of monomeric pramlintide suggests that pharmacokinetics observed for the co-formulation will be well preserved in future translation to humans. Together these results suggest that the co-formulation has the potential to improve mealtime glucose management and reduce patient burden in the treatment of diabetes.

AM833 Is a Novel Agonist of Calcitonin Family G Protein-Coupled Receptors: Pharmacological Comparison with Six Selective and Nonselective Agonists

Obesity and associated comorbidities are a major health burden, and novel therapeutics to help treat obesity are urgently needed. There is increasing evidence that targeting the amylin receptors (AMYRs), heterodimers of the calcitonin G protein-coupled receptor (CTR) and receptor activity-modifying proteins, improves weight control and has the potential to act additively with other treatments such as glucagon-like peptide-1 receptor agonists. Recent data indicate that AMYR agonists, which can also independently activate the CTR, may have improved efficacy for treating obesity, even though selective activation of CTRs is not efficacious. AM833 (cagrilintide) is a novel lipidated amylin analog that is undergoing clinical trials as a nonselective AMYR and CTR agonist. In the current study, we have investigated the pharmacology of AM833 across 25 endpoints and compared this peptide with AMYR selective and nonselective lipidated analogs (AM1213 and AM1784), and the clinically used peptide agonists pramlintide (AMYR selective) and salmon CT (nonselective). We also profiled human CT and rat amylin as prototypical selective agonists of CTR and AMYRs, respectively. Our results demonstrate that AM833 has a unique pharmacological profile across diverse measures of receptor binding, activation, and regulation. SIGNIFICANCE STATEMENT: AM833 is a novel nonselective agonist of calcitonin family receptors that has demonstrated efficacy for the treatment of obesity in phase 2 clinical trials. This study demonstrates that AM833 has a unique pharmacological profile across diverse measures of receptor binding, activation, and regulation when compared with other selective and nonselective calcitonin receptor and amylin receptor agonists. The present data provide mechanistic insight into the actions of AM833.

Poly(ADP-Ribose) Polymerase Inhibitors for Arsenic Trioxide-Resistant Acute Promyelocytic Leukemia: Synergistic In Vitro Antitumor Effects with Hypomethylating Agents or High-Dose Vitamin C

Arsenic trioxide (ATO) is an anticancer agent used for the treatment ofacute promyelocytic leukemia (APL). However, 5%-10% of patients fail to respond or experience disease relapse. Based on poly(ADP-ribose) polymerase (PARP) 1 involvement in the processing of DNA demethylation, here we have tested the in vitro susceptibility of ATO-resistant clones (derived from the human APL cell line NB4) to PARP inhibitors (PARPi) in combination with hypomethylating agents (azacitidine and decitabine) or high-dose vitamin C (ascorbate), which induces 5-hydroxymethylcytosine (5hmC)-mediated DNA demethylation. ATO-sensitive and -resistant APL cell clones were generated and initially analyzed for their susceptibility to five clinically used PARPi (olaparib, niraparib, rucaparib, veliparib, and talazoparib). The obtained PARPi IC50 values were far below (olaparib and niraparib), within the range (talazoparib), or above (rucaparib and veliparib) the C max reported in patients, likely as a result of differences in the mechanisms of their cytotoxic activity. ATO-resistant APL cells were also susceptible to clinically relevant concentrations of azacitidine and decitabine and to high-dose ascorbate. Interestingly, the combination of these agents with olaparib, niraparib, or talazoparib resulted in synergistic antitumor activity. In combination with ascorbate, PARPi increased the ascorbate-mediated induction of 5hmC, which likely resulted in stalled DNA repair and cytotoxicity. Talazoparib was the most effective PARPi in synergizing with ascorbate, in accordance with its marked ability to trap PARP1 at damaged DNA. These findings suggest that ATO and PARPi have nonoverlapping resistance mechanisms and support further investigation on PARPi combination with hypomethylating agents or high-dose ascorbate for relapsed/ATO-refractory APL, especially in frail patients. SIGNIFICANCE STATEMENT: This study found that poly(ADP-ribose) inhibitors (PARPi) show activity as single agents against human acute promyelocytic leukemia cells resistant to arsenic trioxide at clinically relevant concentrations. Furthermore, PARPi enhance the in vitro efficacy of azacitidine, decitabine, and high-dose vitamin C, all agents that alter DNA methylation. In combination with vitamin C, PARPi increase the levels of 5-hydroxymethylcytosine, likely as a result of altered processing of the oxidized intermediates associated with DNA demethylation.

A contemporary biological pathway of islet amyloid polypeptide for the management of diabetic dementia

Major challenges of dealing elder patients with diabetes mellitus (DM) are the individualization of consideration in persons with various comorbid types of conditions. In spite of the fact that microvascular and macrovascular problems associated with DM are well documented, there is only a few numbers of reports viewing different conditions, for example, cognitive dysfunction. Cognitive dysfunction is of specific significance due to its effect on self-care and quality of life. All in all, the etiology of cognitive dysfunction in the maturing populace is probably going to be the grouping of ischemic and degenerative pathology. It is likewise trusted that Hyperglycemia is engaged with the system of DM-related cognitive dysfunction. At present, it isn't certain in the case of enhancing glycemic control or utilizing therapeutic agents can enhance the risk of cognitive decay. Amylin was later characterized as an amyloidogenic peptide, confined from a beta cell tumor and called islet amyloid polypeptide (IAPP), and after that, amylin. Conversely, we investigate the beneficial role and hypothesizing the mechanism of amylin related expanding the level and activation of CGRP receptor to enhance the cognition declination amid diabetic dementia.

Amylin in Alzheimer's disease: Pathological peptide or potential treatment?

Alzheimer's disease (AD) is a neurodegenerative disease for which we currently lack effective treatments or a cure. The pancreatic peptide hormone amylin has recently garnered interest as a potential pharmacological target for the treatment of AD. A number of studies have demonstrated that amylin and amylin analogs like the FDA-approved diabetes drug pramlintide can reduce amyloid burden in the brain and improve cognitive symptoms of AD. However, other data suggest that amylin may have pathological effects in AD due to its propensity to misfold and aggregate under certain conditions. Here, the literature supporting a beneficial versus harmful role of amylin in AD is reviewed. Additionally, several critical gaps in the literature are discussed, such as our limited understanding of the amylin system during aging and in disease states, as well as complexities of amylin receptor signaling and of changing pathophysiology during AD progression that might underlie the seemingly conflicting or contradictory results in the amylin/AD literature. This article is part of the Special Issue entitled 'Metabolic Impairment as Risk Factors for Neurodegenerative Disorders.'

IAPP and type 1 diabetes: implications for immunity, metabolism and islet transplants

Islet amyloid polypeptide (IAPP), the main component of islet amyloid in type 2 diabetes and islet transplants, is now recognized as a contributor to beta cell dysfunction. Increasingly, evidence warrants its investigation in type 1 diabetes owing to both its immunomodulatory and metabolic actions. Autoreactive T cells to IAPP-derived epitopes have been described in humans, suggesting that IAPP is an islet autoantigen in type 1 diabetes. In addition, although aggregates of IAPP have not been implicated in type 1 diabetes, they are potent pro-inflammatory stimuli to innate immune cells, and thus, could influence autoimmunity. IAPP aggregates also occur rapidly in transplanted islets and likely contribute to islet transplant failure in type 1 diabetes through sterile inflammation. In addition, since type 1 diabetes is a disease of both insulin and IAPP deficiency, clinical trials have examined the potential benefits of IAPP replacement in type 1 diabetes with the injectable IAPP analogue, pramlintide. Pramlintide limits postprandial hyperglycemia by delaying gastric emptying and suppressing hyperglucagonemia, underlining the possible role of IAPP in postprandial glucose metabolism. Here, we review IAPP in the context of type 1 diabetes: from its potential involvement in type 1 diabetes pathogenesis, through its role in glucose metabolism and use of IAPP analogues as therapeutics, to its potential role in clinical islet transplant failure and considerations in this regard for future beta cell replacement strategies.

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.

Amylin-mediated control of glycemia, energy balance, and cognition

Amylin, a peptide hormone produced in the pancreas and in the brain, has well-established physiological roles in glycemic regulation and energy balance control. It improves postprandial blood glucose levels by suppressing gastric emptying and glucagon secretion; these beneficial effects have led to the FDA-approved use of the amylin analog pramlintide in the treatment of diabetes mellitus. Amylin also acts centrally as a satiation signal, reducing food intake and body weight. The ability of amylin to promote negative energy balance, along with its unique capacity to cooperatively facilitate or enhance the intake- and body weight-suppressive effects of other neuroendocrine signals like leptin, have made amylin a leading target for the development of novel pharmacotherapies for the treatment of obesity. In addition to these more widely studied effects, a growing body of literature suggests that amylin may play a role in processes related to cognition, including the neurodegeneration and cognitive deficits associated with Alzheimer's disease (AD). Although the function of amylin in AD is still unclear, intriguing recent reports indicate that amylin may improve cognitive ability and reduce hallmarks of neurodegeneration in the brain. The frequent comorbidity of diabetes mellitus and obesity, as well as the increased risk for and occurrence of AD associated with these metabolic diseases, suggests that amylin-based pharmaceutical strategies may provide multiple therapeutic benefits. This review will discuss the known effects of amylin on glycemic regulation, energy balance control, and cognitive/motivational processes. Particular focus will be devoted to the current and/or potential future clinical use of amylin pharmacotherapies for the treatment of diseases in each of these realms.

Role of Amylin in Type 1 and Type 2 Diabetes

Purpose

The pathophysiology of diabetes has historically focused on alterations in insulin secretion and function; however, diabetes involves multiple hormonal alterations, including abnormal regulation of amylin. This review discusses the physiologic functions of amylin in glucose homeostasis and the rationale for amylin replacement in type 1 and 2 diabetes. The use of pramlintide, a synthetic amylin analog, is also discussed.

Conclusions

Amylin, formed primarily in pancreatic islet β cells, is cosecreted with insulin in response to caloric intake. Patients with type 1 diabetes have lower baseline amylin serum concentrations, and amylin response to caloric intake is absent. Patients with type 2 diabetes requiring insulin also have a diminished amylin response to caloric intake, potentially related to the degree of β-cell impairment. Key physiologic functions of amylin in maintaining glucose homeostasis include suppressing glucagon release in response to caloric intake, delaying the rate of gastric emptying, and stimulating the satiety center in the brain to limit caloric intake. Pramlintide is indicated for adults with type 1 and 2 diabetes who have not achieved adequate glucose control despite optimal insulin therapy. As an adjunct to insulin therapy, pramlintide demonstrated significant reductions in A1C in patients with type 1 and 2 diabetes, with favorable effects on body weight. It is administered subcutaneously before each major meal. There is an increased risk of hypoglycemia with insulin when used in combination with pramlintide. Other adverse effects may include nausea, vomiting, anorexia, reduced appetite, and headache. Proper patient selection and education are essential to successful pramlintide use.

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.

Novel therapies for the management of type 2 diabetes mellitus: part 1. pramlintide and bromocriptine-QR

Several classes of antidiabetic agents have been introduced into the market place over the past dozen years. As our understanding of the underlying pathophysiology of type 2 diabetes has advanced, attempts have been made to address these defects specifically. This brief review focuses on our experience with two such pharmacological approaches: (i) a synthetic amylin analog addressing amylin deficiency; and (ii) a dopaminergic agonist, focused on enhancing the lowered dopaminergic tone in patients with type 2 diabetes. Importantly, the use of these agents is not associated with hypoglycemia or weight gain.

Effect of pramlintide on prandial glycemic excursions during closed-loop control in adolescents and young adults with type 1 diabetes

OBJECTIVE

Even under closed-loop (CL) conditions, meal-related blood glucose (BG) excursions frequently exceed target levels as a result of delays in absorption of insulin from the subcutaneous site of infusion. We hypothesized that delaying gastric emptying with preprandial injections of pramlintide would improve postprandial glycemia by allowing a better match between carbohydrate and insulin absorptions.

RESEARCH DESIGN AND METHODS

Eight subjects (4 female; age, 15-28 years; A1C, 7.5 ± 0.7%) were studied for 48 h on a CL insulin-delivery system with a proportional integral derivative algorithm with insulin feedback: 24 h on CL control alone (CL) and 24 h on CL control plus 30-μg premeal injections of pramlintide (CLP). Target glucose was set at 120 mg/dL; timing and contents of meals were identical on both study days. No premeal manual boluses were given. Differences in reference BG excursions, defined as the incremental glucose rise from premeal to peak, were compared between conditions for each meal.

RESULTS

CLP was associated with overall delayed time to peak BG (2.5 ± 0.9 vs. 1.5 ± 0.5 h; P < 0.0001) and reduced magnitude of glycemic excursion (88 ± 42 vs. 113 ± 32 mg/dL; P = 0.006) compared with CL alone. Pramlintide effects on glycemic excursions were particularly evident at lunch and dinner, in association with higher premeal insulin concentrations at those mealtimes.

CONCLUSIONS

Pramlintide delayed the time to peak postprandial BG and reduced the magnitude of prandial BG excursions. Beneficial effects of pramlintide on CL may in part be related to higher premeal insulin levels at lunch and dinner compared with breakfast.

Hepatic steatosis in type 1 diabetes

Islet autoimmunity in type 1 diabetes results in the loss of the pancreatic β-cells. The consequences of insulin deficiency in the portal vein for liver fat are poorly understood. Under normal conditions, the portal vein provides 75% of the liver blood supply. Recent studies suggest that non-alcoholic fatty liver disease (NAFLD) may be more common in type 1 diabetes than previously thought, and may serve as an independent risk marker for some chronic diabetic complications. The pathogenesis of NAFLD remains obscure, but it has been hypothesized that hepatic fat accumulation in type 1 diabetes may be due to lipoprotein abnormalities, hyperglycemia-induced activation of the transcription factors carbohydrate response element-binding protein (ChREBP) and sterol regulatory element-binding protein 1c (SREBP-1c), upregulation of glucose transporter 2 (GLUT2) with subsequent intrahepatic fat synthesis, or a combination of these mechanisms. Novel approaches to non-invasive determinations of liver fat may clarify the consequences for liver metabolism when the pancreas has ceased producing insulin. This article aims to review the factors potentially contributing to hepatic steatosis in type 1 diabetes, and to assess the feasibility of using liver fat as a prognostic and/or diagnostic marker for the disease. It provides a background and a case for possible future studies in the field.

Novel strategy for the use of leptin for obesity therapy

INTRODUCTION

Obesity is a chronic disease and a major global health challenge. Apart from bariatric surgery, which is costly and not without risk, there are currently no successful long-term treatment options for obesity. The history of pharmacological agents for obesity has been turbulent with many examples of drugs being removed from the market due to significant side effects. Orlistat and sibutramine (the latest drugs on the market) provide only modest weight loss and are both associated with high attrition rates due to intolerable side effects. Furthermore, sibutramine was recently withdrawn from the market. There is a need for the development of safe and efficacious drug treatments for obesity.

AREAS COVERED

This review covers the history of leptin therapy as an orphan drug, leptin-replacement therapy as a treatment for obesity, preclinical studies showing the efficacy of leptin/amylin combination and finally, the very promising early clinical findings using pramlintide/meteleptin combination therapy in overweight to obese individuals.

EXPERT OPINION

Combination pharmacological therapy, such as pramlintide/metreleptin, for the treatment of obesity is very promising and is supported by encouraging weight loss results and improvement in metabolic makers in early-phase clinical studies. However, the latest randomized clinical trial on pramlintide/metreleptin was recently stopped due to safety concerns.

Pramlintide and the treatment of diabetes: a review of the data since its introduction

INTRODUCTION

Postprandial glucose excursions negatively affect glycemic control and markers of cardiovascular health. Pramlintide, an amylinomimetic, is approved for treatment of elevated postprandial glucose levels in type 1 and type 2 diabetes mellitus.

AREAS COVERED

A literature search of PubMed was conducted to locate articles (up to January 2011) pertaining to original preclinical and clinical research and reviews of amylin and pramlintide. Additional sources were selected from reference lists within articles obtained through the original literature search and from the internet. This article describes the known effects of endogenous amylin and the pharmacodynamics, pharmacokinetics and clinical efficacy of pramlintide. Drug-drug interactions and safety and tolerability are also reviewed.

EXPERT OPINION

Pramlintide significantly reduces hemoglobin A(1c) and body weight in patients with type 1 and type 2 diabetes mellitus. Newer research is focusing on weight loss effects of pramlintide and pramlintide plus metreleptin in nondiabetic obese individuals. Preliminary results of these studies are discussed.

Twenty-four-hour simultaneous subcutaneous Basal-bolus administration of insulin and amylin in adolescents with type 1 diabetes decreases postprandial hyperglycemia

CONTEXT

The purpose of this study was to examine the effect of continuous sc replacement of amylin and insulin for a 24-h period on glucose homeostasis in adolescents with type 1diabetes.

METHODS

Thirteen adolescents with type 1 diabetes on insulin pump therapy participated in a randomized, controlled, crossover design study comparing continuous sc insulin monotherapy (part A) vs. continuous sc insulin and pramlintide infusion (part B). In part A, basal and bolus insulin infusion was per prescribed home regimen. In part B, the basal insulin infusion was the same as part A, but prandial insulin boluses were reduced by 20%. Basal and prandial bolus pramlintide were administered simultaneously via another pump. All boluses were given as a dual wave.

RESULTS

The study regimen resulted in a 26% reduction in postprandial hyperglycemia as compared to insulin monotherapy (area under the curve, 600 min, 2610 +/- 539 vs. 692 +/- 861 mg/liter . min) (P < 0.008). Glucagon concentrations were suppressed postprandially (P < 0.003) but not in the postabsorptive state, whereas plasma insulin concentrations were unchanged.

CONCLUSIONS

Simultaneous continuous sc pramlintide and insulin infusion has the potential of improving glucose concentrations by way of physiological replacement.

Gastric emptying and postprandial glucose excursions in adolescents with type 1 diabetes

Because amylin is co-secreted with insulin from beta cells, patients with type 1 diabetes (T1DM) are deficient in both insulin and amylin. Amylin delays gastric emptying and suppresses glucagon in the postprandial period. Hence, we hypothesized that children with complication-naive T1DM have accelerated gastric emptying in response to a mixed meal because of amylin deficiency. Amylin, glucagon, insulin, glucose, and gastric emptying were measured in seven T1DM and in eight control subjects without diabetes. Subjects with T1DM had markedly elevated glucose concentrations when compared with controls (p < 0.0001). Amylin concentrations as predicted were lower in T1DM compared with those in controls (p < 0.0001). Insulin did not peak in the immediate postprandial period in T1DM when compared with controls (p < 0.0001). Glucagon concentrations did not significantly differ between groups. Interestingly, gastric velocity was delayed in patients with T1DM compared with controls (p < 0.01). In conclusion, subjects with T1DM do have amylin deficiency but this is not associated with accelerated gastric emptying as we had hypothesized but rather with delayed gastric emptying. Factors other than amylin play a role in control of gastric motility in T1DM. Subcutaneous insulin delivery fails to reach adequate concentrations in the postprandial period to curtail peak glucose concentration in T1DM.

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.

The role of prandial pramlintide in the treatment of adolescents with type 1 diabetes

Pramlintide, a synthetic analog of amylin, improves postprandial hyperglycemia. We compared subcutaneous (s.c.) pramlintide injection with square wave pramlintide infusion in adolescents with type 1 diabetes (T1DM). Eight subjects with T1DM underwent two randomized studies. Subcutaneous pramlintide (dose = 5 microg/unit of insulin) bolus, was given one time and another time, the same dose was given as a 120-min s.c. infusion. Insulin dose was constant between studies. Gastric emptying was assessed with oral acetaminophen and [l-13C]glucose in meal. Plasma glucagon, pramlintide, and insulin concentrations were measured. Insulin concentrations (p < 0.99) between pramlintide injection versus infusion were similar; however, glucose concentrations were different (p < 0.0001), with the absence of hypoglycemia during pramlintide infusion [AUC (0-120 min) -0.07 +/- 0.2 versus 1.05 +/- 0.24 mg * h/dL (p < 0.0088)]. Insulin-only administration resulted in postprandial hyperglycemia and late postprandial hypoglycemia (p < 0.0001). Two subjects experienced hypoglycemia with pramlintide injection. Pramlintide bolus caused pronounced glucagon suppression (p < 0.0003) and delayed gastric emptying as ([13CO2] p < 0.0003 and acetaminophen p < 0.01) compared with infusion. We conclude that pramlintide bolus may result in an increase in risk of immediate postprandial hypoglycemia. Further modifications in pramlintide delivery are indicated before it can be safely used in children.

Pharmacological actions of the peptide hormone amylin in the long-term regulation of food intake, food preference, and body weight

The ability of amylin to reduce acute food intake in rodents is well established. Longer-term administration in rats (up to 24 days) shows a concomitant reduction in body weight, suggesting energy intake plays a significant role in mediating amylin-induced weight loss. The current set of experiments further explores the long-term effects of amylin (4–11 wk) on food preference, energy expenditure, and body weight and composition. Furthermore, we describe the acute effect of amylin on locomotor activity and kaolin consumption to test for possible nonhomeostatic mechanisms that could affect food intake. Four-week subcutaneous amylin infusion of high-fat fed rats (3–300 μg·kg−1·day−1) dose dependently reduced food intake and body weight gain (ED50for body weight gain = 16.5 μg·kg−1·day−1). The effect of amylin on body weight gain was durable for up to 11 wks and was associated with a specific loss of fat mass and increased metabolic rate. The body weight of rats withdrawn from amylin (100 μg·kg−1·day−1) after 4 wks of infusion returned to control levels 2 wks after treatment cessation, but did not rebound above control levels. When self-selecting calories from a low- or high-fat diet during 11 wks of infusion, amylin-treated rats (300 μg·kg−1·day−1) consistently chose a larger percentage of calories from the low-fat diet vs. controls. Amylin acutely had no effect on locomotor activity or kaolin consumption at doses that decreased food intake. These results demonstrate pharmacological actions of amylin in long-term body weight regulation in part through appetitive-related mechanisms and possibly via changes in food preference and energy expenditure.

Pramlintide acetate in the treatment of Type 2 and Type 1 diabetes mellitus

Maintenance of glucose homeostasis involves the interplay of multiple glucoregulatory factors, including the pancreatic β-cell hormones insulin and amylin. Amylin, a neuroendocrine hormone, is secreted in response to nutrient intake and suppresses postprandial glucagon secretion, helps regulate gastric emptying, and reduces food intake. Patients with diabetes are deficient in both insulin and amylin - contributing to postprandial hyperglycemia. Pramlintide, an analogue of amylin, is the active ingredient in the SYMLIN^® (pramlintide acetate) injection. SYMLIN is indicated as an adjunctive treatment for insulin-using patients with diabetes and works through mechanisms similar to those of amylin. Clinical trials have demonstrated that pramlintide therapy improves postprandial glucose control, lowers A1C, and is accompanied by a reduction in body weight. Mild-to-moderate nausea and an increased risk of insulin-induced severe hypoglycemia have been the most common side effects. These side effects can be mitigated by gradual pramlintide dose escalation during treatment initiation and proactive mealtime insulin dose reduction upon initiation of pramlintide therapy.

The physiology of amylin and insulin: maintaining the balance between glucose secretion and glucose uptake

Glucose homeostasis is accomplished through intricate, and arguably, elegant interactions among several organs and hormones. Historically, glucose homeostasis has been viewed somewhat narrowly--insulin from pancreatic beta cells regulated glucose disposal, while glucagon from pancreatic alpha [corrected] cells regulated glucose appearance during fasting states. But more recent characterization and understanding of the role of incretin hormones from the gut--notably, glucagon-like peptide 1 and gastric inhibitory polypeptide--and amylin from pancreatic beta cells has led to a more complete model of glucose homeostasis. Furthermore, availability of pharmacologic agents to replace, mimic, or enhance the actions of these hormones allows application of this more complete model of glucose homeostasis to the treatment of type 1 and type 2 diabetes. This article provides an overview of the role of the pancreatic hormone amylin in glucose homeostasis and of Pramlintide, a analogue of native amylin, recently approved as adjunct therapy to insulin in people with type 1 and type 2 diabetes.

Pramlintide Acetate

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Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. If you would like information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The July 2005 monograph topics are exenatide injection, inhaled insulin, fluocinolone acetonide intravitreal implant, tigecycline, and medroxyprogesterone acetate injectable suspension. The DUE is on exenatide injection.

Ghrelin, peptide YY, glucose-dependent insulinotropic polypeptide, and hunger responses to a mixed meal in anorexic, obese, and control female adolescents

To determine whether peptide YY (PYY), ghrelin, glucose-dependent insulinotropic polypeptide (GIP), and satiety responses to food intake are impaired in anorexia or obesity, we studied 30 female adolescents with anorexia nervosa [body mass index (BMI) 16.3 kg/m2], obesity (BMI 34.3 kg/m2), or normal weight (BMI 20.2 kg/m2). PYY, ghrelin, GIP, insulin, and glucose concentrations and four markers of satiety were measured for 240 min after a mixed meal. The area under the curve for glucose was similar in obese (OB) and normal-weight control (C) subjects but was 15% lower in anorexic (AN) subjects. The area under the curve for insulin was 47% lower in AN and 87% higher in OB subjects, compared with C subjects. After the meal, PYY increased significantly in C (+41%, P < 0.05) but not in AN or OB adolescents. Ghrelin concentrations were highest in AN subjects and lowest in the OB group, compared with C subjects and fell significantly by 25% in all three groups. GIP concentrations were lower in AN subjects throughout the test and increased in all three groups after the mixed meal. AN adolescents reported being less hungry than OB and C adolescents. There was a negative correlation between fasting ghrelin (but not PYY or GIP) and BMI and insulin (r2= 0.33) and a positive correlation between the decrease in hunger 15 min after the meal and PYY concentrations at 15 min (r2= 0.20). In conclusion, the blunted PYY response to a meal in OB adolescents suggests that PYY plays a role in the pathophysiology of obesity. Ghrelin is unlikely to play a causal role in anorexia nervosa or obesity. The lower GIP observed in AN subjects despite a similar caloric intake may appropriately prevent an excessive insulin response in these patients.

Effects of pramlintide on postprandial glucose excursions and measures of oxidative stress in patients with type 1 diabetes

OBJECTIVE

Oxidative stress has been shown to be increased in the postprandial period in patients with diabetes and has been implicated in the pathogenesis of micro- and macrovascular complications. The aim of this post hoc analysis was to assess the effects of pramlintide, an amylin analog shown to reduce postprandial glucose excursions in patients with diabetes, on markers of oxidative stress in the postprandial period.

RESEARCH DESIGN AND METHODS

In a randomized, single-blind, placebo-controlled, crossover study, 18 evaluable subjects with type 1 diabetes underwent two standardized breakfast meal tests and received pramlintide or placebo in addition to their preprandial insulin. The plasma concentrations of glucose and markers of oxidative stress (nitrotyrosine, oxidized LDL [ox-LDL], and total radical-trapping antioxidant parameter [TRAP]) were measured at baseline and during the 4-h postprandial period.

RESULTS

Compared with placebo, pramlintide treatment significantly reduced postprandial excursions of glucose, nitrotyrosine, and ox-LDL and prevented a decline in TRAP (P < 0.03 for all comparisons). Correlation analyses adjusted for treatment revealed a significant association between postprandial mean incremental area under the curve from 0 to 4 h (AUC(0-4 h)) for glucose and postprandial mean incremental AUC(0-4 h) for each measure of oxidative stress (r = 0.75, 0.54, and -0.63 for nitrotyrosine, ox-LDL, and TRAP, respectively; P < 0.001 for all correlations).

CONCLUSIONS

These findings indicate that the postprandial glucose-lowering effect of pramlintide in type 1 diabetes is associated with a significant reduction in postprandial oxidative stress.

Inhibition of gastric emptying

In studies aimed at defining the role of amylin in glucose control, elevations of postprandial glucose concentration were blunted in subjects infused with the human amylin analog, pramlintide (Kolterman et al., 1995, 1996). An effect similar to blunt glucose excursions was observed by Brown and others during infusions of amylin in dogs trained to drink glucose (Brown et al., 1994). The effect of pramlintide in humans was present when glucose was administered orally, but not when administered intravenously, suggesting that the effect was due to a deceleration of glucose uptake from the meal, rather than an acceleration of its metabolism (Kolterman et al., 1995). Since amylin did not affect the rate of glucose transit across exteriorized gut loops (Young and Gedulin, 2000), it was proposed that blunting of postprandial glucose profiles could reflect effects on gastric emptying. Rates of gastric emptying have been determined using three different approaches: (1) by measurement of remnant dye found in acutely excised stomachs, (2) by the systemic appearance of labels that are not significantly absorbed until they leave the stomach (e.g., labeled glucose, acetaminophen, 13C-labeled volatiles), and (3) by following the passage of radiolabeled meal components scintigraphically, with a gamma-camera. Amylin and/or pramlintide were shown to potently inhibit gastric emptying by the first method in animals (Clementi et al., 1996; Young et al., 1995a, 1996b), by the second method in animals (Gedulin et al., 1995; Young et al., 1995a, 1996a) and in humans, including those with type 1 and type 2 diabetes (Burrell et al., 2003b; Hücking et al., 2000; Kong et al., 1998; Lee et al., 2000; Vella et al., 2002), and by scintigraphy in patients with type 1 diabetes (Kong et al., 1997, 1998) and in nondiabetic subjects (Samsom et al., 2000). Depending upon dose, responses ranged from a slowing of emptying rate (e.g., by approximately 50%) to a complete cessation. In rats, amylin was 15-fold more potent on a molar basis than glucagon-like peptide-1 (GLP-1) and 20-fold more potent than cholecystokinin octapeptide (CCK-8) for inhibition of gastric emptying (Young et al., 1996b). It was the most potent mammalian peptide of 21 tested for this action (Gedulin et al., 1996b). Amylin inhibition of gastric emptying appears to be mediated by a central mechanism (Clementi et al., 1996; Dilts et al., 1997; Young et al.,2000). An intact vagus nerve (Jodka et al., 1996) and an intact area postrema (Edwards et al., 1998) are required for the effect. In rats that underwent total subdiaphragmatic vagotomy or surgical ablation of the area postrema, amylin was no longer effective at inhibiting gastric emptying (Edwards et al.,1998). The effect of amylin and amylin agonists (including pramlintide) to inhibit gastric emptying was reversed by insulin-induced hypoglycemia (Gedulin and Young, 1998; Gedulin et al., 1997b,c,d; Young et al., 1996a). This suggests the existence of a glucose-sensitive "fail-safe" mechanism that safeguards against severe hypoglycemia; nutrients ingested in response to the hunger that accompanies hypoglycemia can pass rapidly through the stomach for immediate digestion and absorption, unimpaired by the physiological restraint of amylin that would normally prevail at normal glucose concentrations. It seems likely that amylinergic control of gastric emptying is mediated via neurons in the area postrema shown in brain slices to be activated by amylin, and inhibited by low glucose (Riediger et al., 1999). Such neurons have been proposed to mediate glucoprivic gut reflexes (Adachi et al., 1995).

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.

Effect of pramlintide on symptom, catecholamine, and glucagon responses to hypoglycemia in healthy subjects

Pramlintide is an analog of the human glucoregulatory hormone amylin. Previous studies have shown no clear evidence that pramlintide modifies the response to insulin-induced hypoglycemia; however, a detailed assessment of responses at hypoglycemic thresholds has not been conducted. To further test the effect of pramlintide on symptom, catecholamine, and glucagon responses, a 3-step hypoglycemic clamp was investigated in healthy volunteers. In a randomized, double-blind, placebo-controlled, crossover study, 18 healthy subjects without diabetes received subcutaneous premeal injections of either placebo or 60 microg pramlintide 3 times daily for 5 consecutive days. On day 6, subjects received study drug with breakfast and, after a 7-hour fast, were connected to a Biostator for a 3-step, 3-hour clamp experiment (insulin infusion rate: 1.0 mU/kg/min; blood glucose targets: 70, 55, and 45 mg/dL). An intravenous (IV) infusion of pramlintide (16 microg/h) or placebo was initiated at t = 60 minutes. At the end of each 60-minute clamp step, autonomic (sweating, palpitations, hunger, etc) and neuroglycopenic (confusion, headache, odd behavior, etc) symptoms were assessed using a validated visual analog scale questionnaire. Blood samples were collected at 30-minute intervals for measurement of plasma glucose, insulin, pramlintide, catecholamine, and glucagon concentrations. Intraindividual and group mean responses showed that autonomic symptoms and plasma catecholamine and glucagon concentrations increased progressively during the clamp, with no discernible differences between pramlintide and placebo treatments. Group means for catecholamines at 60 minutes were: epinephrine 233 +/- 42, 892 +/- 85, 2,340 +/- 302 and 202 +/- 25, 774 +/- 114, 2,751 +/- 404 pg/mL and norepinephrine 1,138 +/- 86, 1,236 +/- 77, 1,721 +/- 158 and 1,278 +/- 108, 1,259 +/- 109, 1,580 +/-136 pg/mL (+/- SEM) for placebo- and pramlintide-treated groups at 70, 55, and 45 mg/dL glucose, respectively. Group means for glucagon were 72 +/- 6.3, 98 +/- 11.1, 130 +/- 14.7 and 63 +/- 3.6, 92 +/- 9.4, 120 +/- 16.0 pmol/L (+/- SEM) for placebo- and pramlintide-treated groups at 70, 55, and 45 mg/dL glucose, respectively. These results showed that pramlintide did not impair the symptom, catecholamine, and glucagon responses to insulin-induced hypoglycemia in healthy subjects.

Pramlintide reduces postprandial glucose excursions when added to regular insulin or insulin lispro in subjects with type 1 diabetes: a dose-timing study

OBJECTIVE

To assess the postprandial glucose-lowering effect of the human amylin analog pramlintide when given with either regular insulin or insulin lispro in subjects with type 1 diabetes, with an emphasis on the optimal dose timing relative to meals.

RESEARCH DESIGN AND METHODS

In this randomized, single-blind, placebo-controlled, five-way crossover study, 19 subjects with type 1 diabetes using regular insulin and 21 subjects with type 1 diabetes using insulin lispro underwent five consecutive mixed meal tests. In randomized order, subjects received subcutaneous injections of placebo at -15 min or 60 microg pramlintide at -15, 0, +15, or +30 min relative to the meal after an overnight fast. Regular insulin or insulin lispro was injected at -30 and 0 min, respectively, at doses that were adjusted appropriately for both the content of the standardized meal and the anticipated effects of pramlintide. Plasma glucose concentrations were measured before and during the 4-h postmeal period.

RESULTS

In both the regular insulin and insulin lispro groups, pramlintide injections at all four time points lowered the postprandial glucose excursion (36 to >100% reduction in incremental area under the concentration time curve from 0 to 4 h (AUC(0-4 h)) compared with placebo. However, only preprandial injections of pramlintide (-15 and 0 min) were able to prevent the initial postprandial surge in glucose. The optimal time for pramlintide injection was 0 min, which reduced the postprandial glucose excursion by >100% compared with regular insulin plus placebo (incremental AUC(0-4 h): -0.6 +/- 2.5 vs. 11.0 +/- 2.9 mmolx h(-1) x l(-1), P < 0.0007) and by 75% compared with insulin lispro plus placebo (incremental AUC(0-4 h): 2.5 +/- 2.1 vs. 10.0 +/- 2.5 mmol x h(-1) x l(-1), P < 0.0098). No serious adverse events were reported.

CONCLUSIONS

Pramlintide, given at or just before a meal, reduces the postprandial glucose excursion in subjects with type 1 diabetes, regardless of whether added to regular insulin or a rapid-acting insulin analog.

Weight Effect of Current and Experimental Drugs for Diabetes Mellitus

Two landmark intervention studies, the Diabetes Control and Complications Trial (DCCT) in patients with type 1 diabetes mellitus and the United Kingdom Prospective Diabetes Study (UKPDS) in patients with type 2 diabetes mellitus, have unequivocally demonstrated that intensive diabetes therapy reduces the risk of long-term diabetic complications. As a result, the commonly accepted treatment goal for most patients with diabetes is the achievement and maintenance of glycemic control that is as close to the normal range as safely possible. Important adverse effects of intensive diabetes therapy, particularly when the treatment includes insulin or several of the oral antihyperglycemic agents, are an increased risk of hypoglycemia and undesired weight gain. Improvement of glycemic control with insulin, insulin secretagogues (sulfonylureas, meglitinides), and insulin sensitizers (thiazolidinediones) is often accompanied by weight gain. The etiology of this weight gain is likely multifaceted, including a reduction of glucosuria, increased caloric intake to prevent hypoglycemia, and anabolic effects on adipose tissue. Biguanides and alpha-glucosidase inhibitors have a neutral or even positive effect (decrease) on weight, which may partly be attributable to their non-insulinotropic mechanism of action, a modest effect on satiety, and to their gastrointestinal adverse effect profile. Several antihyperglycemic agents that are currently in clinical development may improve glycemic control in conjunction with weight reduction. These include an analog of the pancreatic beta-cell hormone amylin (pramlintide), as well as glucagon-like peptide-1 (GLP-1) and exendin, and their analogs. Pharmacological agents with antihyperglycemic and positive weight effects have the potential to become important additions to our therapeutic armamentarium, in that they may help to achieve glycemic targets while addressing the long-standing clinical problem of weight gain as an adverse effect of intensive diabetes therapy.

Unresolved challenges with insulin therapy in type 1 and type 2 diabetes: potential benefit of replacing amylin, a second beta-cell hormone

Current insulin therapy still fails to safely restore near-normoglycemia in the majority of patients. Among the barriers to achieving tight long-term glycemic control with insulin in both type 1 and type 2 diabetes are an increased risk of hypoglycemia, undesired weight gain, and a failure to normalize postprandial hyperglycemia and excessive unpredictable diurnal glucose fluctuations. Amylin is a second beta-cell hormone that is cosecreted with insulin in response to meals, and is deficient in patients with type 1 and insulin-requiring type 2 diabetes. Preclinical studies indicate that amylin acts as a neuroendocrine hormone that complements the effects of insulin in postprandial glucose regulation by suppressing postprandial glucagon secretion and slowing the rate of nutrient delivery from the stomach to the small intestine. Human amylin is not optimal for replacement therapy because of its propensity to aggregate; thus, pramlintide, a soluble, nonaggregating synthetic peptide analog of human amylin, was developed that has potency at least equal to that of human amylin. In clinical studies, subcutaneous injections of pramlintide prior to meals, in addition to insulin therapy, significantly reduced postprandial glucose excursions and lowered HbA(1c) levels in patients with type 1 and type 2 diabetes. The improvement in long-term glycemic control was associated with a significant reduction in body weight and occurred without increases in total daily insulin use or in overall severe hypoglycemia event rates. Because of this unique spectrum of clinical effects, amylin replacement with pramlintide as an adjunctive therapy to insulin is a promising approach that may fulfill some of the unmet clinical needs of insulin-using patients with type 1 and type 2 diabetes.

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.

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.

Current status and future prospects of parenteral insulin regimens, strategies and delivery systems for diabetes treatment

A strong relationship between long term metabolic control and low frequency of chronic diabetes complications was shown in the Diabetes Control Complication Trial (DCCT). However, the subcutaneous intensive insulin therapy required to achieve the glycemic goals defined by the DCCT led to an unacceptable frequency of severe hypoglycemia and a significant weight gain. This limits the benefits of this therapy and excludes groups of patients such as young children, the elderly or hypoglycemia prone patients. The intensive therapy and self blood glucose monitoring (SMBG) necessary to limit hypoglycemia represent a heavy burden for the patients and their family. Improvements in parenteral insulin therapy are possible by either modifying subcutaneous insulin characteristics (analogs, adjunction of peptides such as amylin, GLP1, IGF1), or by developing better routes of administration and making SMBG easier, which is a key to intensive insulin therapy success. The ultimate goal remains the development of an automated, glucose controlled device.

Present and future perspectives on children with type 1 diabetes

This review presents current achievements in paediatric diabetology and discusses potential new approaches. Recent multinational investigations have demonstrated that in spite of multidisciplinary diabetes care only one-third of young patients with diabetes have an HbA1c below 8%, which is associated with a lower risk for development of secondary complications. Since there is no standard protocol for the optimal treatment of diabetes in children and adolescents, the therapy has to be tailored to the individual child's needs, involving not only paediatricians, but also dieticians, diabetes educators, psychologists and social workers. To improve the current situation a major goal for the next few years appears to be the establishment of standards for structure, process and outcome quality in paediatric diabetology. Future perspectives include possibilities for a cure via islet- or pancreas transplantation or improved pharmacological therapy following the introduction of new types of insulin or other beta cell-related peptides as adjunctive therapy not currently used.

Distribution and kinetics of amylin in humans

The aim of the study was to determine the apparent volume of distribution (VTOT), total body clearance (CL), fractional clearance, and mean residence time (MRT) of the beta-cell hormone amylin. We therefore performed an intravenous injection of 50 micrograms of human synthetic amylin (amlintide) in nine healthy male subjects during suppression of endogenous amylin release by intravenous somatostatin (0.06 microgram.kg-1.min-1). The plasma levels of amylin concentrations over time were analyzed using three-exponential curves. VTOT was 173 +/- 16 ml/kg and was not different from that of insulin reported in the literature (157 ml/kg). MRT was 27.7 +/- 2.1 min and thus two times the reported value for insulin (14.1 min) and C-peptide (16.4 min). CL and fractional CL were 6.2 +/- 0.2 ml.kg-1.min-1 and 0.038 +/- 0.003 min-1, respectively. Fractional CL is therefore definitely lower than that reported for insulin (0.12-0.2 min-1) but is, however, in the range of that of C-peptide (0.05 min-1). In conclusion, clearance of amylin is similar to that reported for C-peptide and much slower than insulin, indicating that the commonly used molar insulin-to-amylin ratio does not reflect the correct relationship of the two peptides.

Peptide hormones: Review of current and emerging uses by nasal delivery

The family of clinically available peptide hormones (PHs) is expanding in an exponential way, and advancement of knowledge of the basic mechanisms of action of PHs has led to multiplication of the possible clinical indications of already known PHs, and appears even more promising for still unknown PHs. A common obstacle to a full routine use of PHs is represented by the fact that PHs cannot be administered by the oral route, since they undergo digestion and inactivation in the gastrointestinal tract and a significant first pass metabolism in the liver. One alternative is represented by intranasal administration of PHs. The intranasal route of administration of PHs is also very attractive because of its convenience, which should assure a good compliance by patients. Luteinizing hormone releasing hormone, the analogues, desmopressin, oxytocin and salmon calcitonin are already marketed for intranasal administration; for salmon calcitonin, studies about bioavailability have been scanty in the past, but should be re-considered in order to fully explore its clinical benefit.Intranasal peptide hormones not yet on the market are insulin, glucagon, growth hormone releasing hormone (GHRH) and GHRP, GH and somatostatin, but the scenario is likely to change in a short period of time. Hexarelin seems very effective and is at a promising stage of development; also, glucagon appears mature enough to undergo extensive clinical evaluation and possibly marketing. The concern is why other peptides have not been further evaluated, as is the case for somatostatin and its analogues.

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

The effects of 4 weeks' administration of pramlintide, an analogue of the human hormone amylin, on blood glucose control in 215 patients with insulin-dependent diabetes mellitus were examined in a 4-week, randomized, double-blind, placebo-controlled, parallel-group trial. Pramlintide was administered subcutaneously prior to meals in four dosing regimens: 30 microg four times per day (breakfast, lunch, dinner, and evening snack), 30 microg three times per day (breakfast, lunch and dinner [BLD]), 30 microg three times per day (breakfast, dinner and evening snack [BDS]), and 60 microg twice per day (breakfast and dinner). After 4 weeks of pramlintide 30 microg four times per day administration, there was a statistically significant reduction in the mean 24 h plasma glucose concentration when compared to placebo (-1.4 +/- 0.5 vs 0.3 +/- 0.5 micromol/l, p = 0.009). Serum fructosamine concentrations were reduced 62 +/- 10 micromol/l in the pramlintide 30 mg four times per day group, 43 +/- 7 micromol/l in the pramlintide 30 microg three times per day (BLD) group, 47 +/- 6 micromol/l in the pramlintide 30 microg three times per day (BDS) group, 46 +/- 7 micromol/l in the pramlintide 60 microg twice per day group, and 29 +/- 8 micromol/l by placebo. The incidence of hypoglycaemia was not different in any pramlintide group compared to the placebo group. Nausea, the most frequent adverse event, subsided after the first week of treatment in the majority of patients. In conclusion, pramlintide improved blood glucose control over a 4-week period without increased hypoglycaemia and was well tolerated. Future studies using a longer period of pramlintide administration with assessment of HbA1c as the measurement of glycaemic control are warranted.

Drug treatment of non-insulin-dependent diabetes mellitus in the 1990s. Achievements and future developments

Non-insulin-dependent diabetes mellitus (NIDDM, type 2 diabetes) is a heterogeneous disease resulting from a dynamic interaction between defects in insulin secretion and insulin action. There are various pharmacological approaches to improving glucose homeostasis, but those currently used in clinical practice either do not succeed in restoring normoglycaemia in most patients or fail after a variable period of time. For glycaemic regulation, 4 classes of drugs are currently available: sulphonylureas, biguanides (metformin), alpha-glucosidase inhibitors (acarbose) and insulin, each of which has a different mode and site of action. These standard pharmacological treatments may be used individually for certain types of patients, or may be combined in a stepwise fashion to provide more ideal glycaemic control for most patients. Adjunct treatments comprise a few pharmacological approaches which may help to improve glycaemic control by correcting some abnormalities frequently associated with NIDDM, such as obesity (serotoninergic anorectic agents) and hyperlipidaemia (benfluorex). There is intensive pharmaceutical research to find new drugs able to stimulate insulin secretion (new sulphonylurea or nonsulphonylurea derivatives, glucagon-like peptide-1), improve insulin action (thiazolidinediones, lipid interfering agents, glucagon antagonists, vanadium compounds) or reduce carbohydrate absorption (miglitol, amylin analogues, glucagon-like peptide-1). Further studies should demonstrate the superiority of these new compounds over the standard antidiabetic agents as well as their optimal mode of administration, alone or in combination with currently available drugs.