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Keywords:

  • glucose;
  • pancreatic polypeptide

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES

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 μg 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 μg t.i.d. (268 ± 37 min, 329 ± 49 min, respectively; P < 0.01]. Postprandial HPP levels were lower in response to 30 and 60 μg 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.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES

Amylin is a 37-amino acid peptide that is colocalized and cosecreted with insulin by the pancreatic beta cells in response to nutrient stimuli.1 Fasting amylin concentrations in healthy subjects range between 4 and 8 pmol L−1; postprandial levels rise two- to three-fold following the ingestion of a mixed meal.2 Amylin and insulin levels rise and fall in parallel in the fasted and fed states and, in the fasting period, amylin secretin follows a pulsatile pattern similar to insulin. In patients with type 1 diabetes mellitus, amylin concentrations are either at the lower end of detection of the assay or are undetectable; in addition, circulating levels of amylin in type 1 diabetes mellitus do not increase after nutrient stimulation.2 Thus, type 1 diabetes is a state of amylin as well as insulin deficiency. In contrast, the levels of amylin in type 2 diabetes parallel those of insulin.3 Thus, amylin concentrations in plasma are elevated in early type 2 diabetes when insulin levels are typically elevated and decrease pari passu with insulin secretion in later stages of type 2 diabetes.4 Thus, as with insulin secretion, the levels of amylin vary with the duration and severity of diabetes as β-cell mass is reduced with progression of diabetes. Based on results in vitro, 5 it has also been suggested that amylin itself may contribute to apoptosis of β cells.

Animal6 and human7,8 studies indicate that amylin slows the rate of nutrient delivery to the small intestine by inhibition of gastric emptying; this inhibition of gastric emptying is avoided during insulin-induced hypoglycaemia,6 which is associated with vagal stimulation. Postprandial glucagon secretion is inhibited during amylin-induced retardation of gastric emptying.9 While these effects may attenuate the postprandial rise in glucose, the clinical application of amylin has been limited by its tendency to self-aggregate, its low solubility, and its tendency to adhere to surfaces [e.g. infusion apparatus10]. These problems were resolved by the development of an analogue, pramlintide.

Pramlintide is a stable, bioactive peptide analogue of amylin that differs in three amino acids;11 alanine in position 25 and serine in positions 28 and 29 are substituted with proline. The pharmacokinetic, pharmacodynamic and biological properties of pramlintide are comparable with those of amylin.11 There is evidence that pramlintide improves glycaemic control (postprandial glucose and glycosylated haemoglobin) in both type 1 and type 2 diabetes mellitus.12,13 In a placebo-controlled, cross-over study conducted in 18 people with type 1 diabetes, pramlintide, 30 or 60 μg b.i.d., improved blood glucose profiles relative to placebo.12 Similar results have been observed in 215 people with type 2 diabetes14 who participated in a 4-week, parallel-group, randomized, placebo-controlled study.

The influence of pramlintide on gastric emptying has been documented in diabetic rats15 and in humans with type 1 diabetes mellitus.7,8 A single dose of 30, 60, or 90 μg pramlintide delayed gastric emptying in humans with type 1 diabetes mellitus.8 The amylin receptor belongs to the group of calcitonin gene-related peptide receptors, which are seven transmembrane domain G-protein coupled receptors;16 this class of receptor is associated with desensitization.17 It is unclear whether loss of effect of gastric emptying occurs with repeated administration of pramlintide in people with diabetes mellitus. In view of the differences in circulating amylin concentrations in type 1 and type 2 diabetes,2,3 we were interested in assessing whether the effects of pramlintide were different in both types.

Studies in rats have suggested that the effects of pramlintide may be centrally mediated by inhibition of vagal function. 9 The mechanism of the inhibitory effect of pramlintide on gastric emptying in people with diabetes mellitus is unknown and was explored in this study by measuring the plasma pancreatic polypeptide levels in response to the test meal.

Thus, the present studies were undertaken to compare the effects of 5 days' treatment with placebo, 30 μg, or 60 μg t.i.d. pramlintide on gastric emptying and postprandial plasma pancreatic polypeptide concentrations in people with type 1 or type 2 diabetes mellitus unassociated with clinically detected complications. We report that the significant effect of pramlintide on gastric emptying does not differ in individuals with type 1 or type 2 diabetes and that pramlintide reduces the normal postprandial increase in circulating levels of pancreatic polypeptide.

MATERIALS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES

Participants

After approval by the Mayo Clinic Institutional Review Board, six volunteers with type 1 diabetes mellitus and 6 with type 2 diabetes mellitus gave written informed consent to participate in the study. Subjects' medical records were screened for documented complications suggestive of retinopathy, nephropathy or neuropathy, and were classified as type 1 or type 2 diabetes as previously described.18 Microalbuminuria was excluded in all patients. However, formal retinal, peripheral nerve and autonomic nerve testing was not performed in these participants. Thirteen people with diabetes mellitus were enrolled in the study. One participant withdrew from the study because of nausea after one dose of the study drug and was replaced with a subject who was randomly assigned treatment. All subjects completed an abridged version of a validated bowel disease questionnaire19 to ensure they had no gastrointestinal symptoms prior to participation. Females of childbearing potential were required to have a negative pregnancy test within 24 h of the onset of treatment. Volunteer characteristics are summarized in Table 1

Table 1.   Participant characteristics (data are mean ± SEM) Thumbnail image of

All participants with type 1 diabetes were treated with multiple daily injections of lys–pro insulin, and a daily injection of long-acting insulin. Two participants with type 2 diabetes were being treated with insulin alone, one with a combination of insulin and metformin, and three were treated with an oral hypoglycaemic agent (glyburide). The analysis presented is based on 12 subjects who received 30 μg t.i.d. pramlintide, 60 μg t.i.d. pramlintide, and placebo in random order; all these participants completed the three treatment periods, gastric emptying and blood sampling studies.

Experimental design

The effect of pramlintide on gastric emptying, glucose concentrations and pancreatic polypeptide response to a standardized meal was evaluated in a double-blind, randomized, placebo-controlled, three-period, crossover, dose–response study. All subjects received placebo, or 30 or 60 μg, pramlintide t.i.d., subcutaneously (s.c.), in random order for 4 days, with a washout period of at least 3 days between each treatment. The duration of treatment was based on prior pharmacokinetic studies that showed stable trough levels by 3–4 days; the 3-day washout period ensured no carry-over of the prior dose in the subsequent treatment period. The subjects self-administered the study medication by s.c. injections within 15 min prior to each meal. All participants were instructed in this technique for self-administration by the nursing staff of the General Clinical Research Center. The injections were administered into the subcutaneous tissue of the anterior abdominal wall. The participants received medication daily for 4 days; the gastric-emptying test was performed on day 5, with the final dose of medication administered 15 min prior to the study meal.

Subjects with type 1 diabetes were admitted to the General Clinical Research Center the night prior to study. Following ingestion of a standard 10 kcal kg−1 meal (55% carbohydrate, 30% fat, and 15% protein), subjects fasted until the commencement of the study test meal. An 18-gauge intravenous cannula was inserted into each forearm and a variable infusion of insulin (0.1 U mL−1 Humulin R; Eli Lilly and Co., Indianapolis, IN, USA) was then initiated in order to maintain euglycaemia throughout the night.20 Participants with type 2 diabetes were admitted on the morning of the study after an overnight fast. Those subjects being treated with insulin were instructed not to take their long-acting insulin preparation the evening prior to admission. Subjects receiving oral medication were asked not to take their oral diabetic medication on the morning of study.

Peripheral blood samples were taken at baseline before the meal and subsequently at 15, 30, 60, 75, 90, 120, 150 and 180 min after meal ingestion. Blood samples were collected in ice-chilled EDTA tubes before centrifugation at 4 °C for 10 min. The plasma was stored at –20 °C until assayed.

Gastric emptying by the [13C]S. platensis breath test method

On the morning of each study, solid phase gastric emptying was determined using a commercial breath test meal [Meretek 13Ceebiscuit™ Meretek Diagnostics, Inc., Nashville, TN, USA21]. This 330-calorie meal includes 120 mL of grape juice (80 kcal), 30 g cream cheese (90 kcal) and a 60-g rye biscuit (160 kcal) enriched with 13C-Spirulina platensis. This is an edible blue-green alga used as a protein source in many parts of the world and sold as a food supplement. Each meal contained 50–60% protein, 30% starch, and 10% lipid. The S. platensis used in this study was grown as a pure monoculture in a closed hydroponics chamber in a medium containing inorganic salts and purged with pure 13CO2. The resultant cells were uniformly labelled with 13C; the natural level of 13C in the environment (about 1%) was raised to 99% in the substrate used. When metabolized, the proteins, carbohydrates and lipids of the S. platensis give rise to respiratory CO2 that is enriched in13C. Because the contents of the algal cells are not freely diffusible, incorporation of labelled S. platensis into a solid-phase meal occurs easily and represents the digestive state of the solid food matrix within which it is contained.

After an overnight fast, breath samples were taken at baseline before the meal and every 15 min for 2 h. Breath samples were collected and stored in duplicate in glass vacutainers using a straw to blow into the bottom of the tube to displace contained air. After re-stoppering the tubes, the 13CO2 breath content was determined in a laboratory (by P.D. Klein, Meretek Diagnostics, Inc.) by isotope ratio mass spectrometry.22,23

Analysis of breath test

The 13C enrichment determined by isotope ratio mass spectrometry was expressed as the delta per mL difference between the 13CO2/12CO2 ratio of the sample and the standard. To calculate the quantity of 13C appearing in breath per unit time, delta over baseline (DOB) was used;

inline image

where 0.0112372 is the isotopic abundance of the limestone standard (Pee Dee Belemnite), and CO2 production was corrected for age, sex, height and weight using the algorithms of Schofield24 as described by Klein et al.25

A generalized linear multiple regression model, previously validated in our laboratory based on simultaneous breath test and scintigraphy,21 was used to estimate gastric emptying t50% using 13C values from breath samples obtained postmeal.

Plasma glucose concentrations

Glucose concentrations were measured by a glucose-oxidase method (Beckman, Inc., Chaska, MN, USA). The mean glucose concentration was calculated for the first 90 min after the meal. Subjects received insulin by continuous, variable intravenous (i.v.) infusion (subjects with type 1 diabetes) or by s.c. insulin injection (subjects with type 2 diabetes) to prevent plasma glucose from rising above 200 mg dL−1. One subject with type 2 diabetes was treated by i.v. administration of 20 mL of 50% dextrose for one episode of hypoglycaemia that occurred 20 min after ingestion of the test meal. To prevent excessive postprandial glycaemic excursions that would possibly affect gastric emptying, all subjects received insulin with their test meal. Subjects with type 1 diabetes received 8 ± 2, 9 ± 2, 4 ± 1 units of insulin on the placebo, 30 μg and 60 μg days, respectively. Subjects with type 2 diabetes received 16 ± 7, 13 ± 5, 8 ± 4 units of insulin on the placebo, 30 μg and 60 μg days, respectively.

Plasma pancreatic polypeptide concentrations

The first hour's postprandial response in plasma pancreatic polypeptide has been used as a surrogate of vagal function in previous studies26–28 and correctly identified all patients with previous surgical vagotomy.26 Studies in primates and dogs also suggest that the early postprandial (up to 90 min) increment in circulating levels of pancreatic polypeptide is under cholinergic29 and, more specifically, vagal30,31 control. Vagotomy has several effects on emptying of gastric contents; typically, liquid emptying is accelerated, while solid emptying is delayed.32 Delivery of nutrient to the duodenum is associated with enteropancreatic reflexes that result in pancreatic polypeptide secretion. Mannon and Taylor33 have summarized the literature thus:

`The early phase of pancreatic polypeptide release after ingestion of a meal represents a summated response to cephalic–vagal stimulation and gastric distension and is largely neurally mediated. By contrast, the more prolonged pancreatic polypeptide response to food largely reflects a complex response to hormonal stimulants and the activation of neural reflexes.'

In previous studies, the increment in pancreatic polypeptide in healthy subjects has been shown to be at least 100 pg mL−1 during the first postprandial hour.27,34 We showed in a previous study that pramlintide results in reduced pancreatic polypeptide levels in the early postprandial period during inhibition of gastric emptying in healthy human subjects34 and hypothesized that the two effects may result from vagal inhibition.

Plasma pancreatic polypeptide concentrations were analysed using a radioimmunoassay kit.35 Using a similar test meal (for calorie and protein content) and radioimmunoassay for pancreatic polypeptide, we observed a change in mean pancreatic polypeptide of 120–180 pg mL−1 in 10 healthy controls.27 The mean pancreatic polypeptide concentration was calculated for the first 90 min after the meal.

Statistical analysis

The distributions of plasma pancreatic polypeptide were summarized (mean ± SEM) by dose group and treatment period at each sampling time point (fasting and postprandial) and plotted separately by period. Gastric emptying was summarized via a generalized linear regression model to estimate t50% for each patient in each treatment group.21

The dose groups were compared using the paired Wilcoxon signed rank test. All data were expressed as means ± SEM because the vast majority of data were normally distributed. Median values were also reported for data that were not normally distributed. An adjustment was made for four pairwise comparisons: (i) both drug doses vs. placebo; (ii) 30 μg dose vs. placebo; (iii) 60 μg dose vs. placebo; and (iv) 30 μg vs. 60 μg dose. Thus, P < 0.01 was considered statistically significant in the pairwise comparisons.

A Spearman rank correlation explored the association between mean (15–90 min) postprandial plasma pancreatic polypeptide concentration and gastric emptying t50%.

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES

Overall study results

Overall study results for each treatment period are summarized in Table 2. A period-by-dose interaction was observed. Thus, pramlintide was more effective both in delaying gastric emptying and in suppressing the release of pancreatic polypeptide in the third period. Overall drug effects were clearly evident and are discussed below for each specific endpoint.

Table 2.   Period-by-dose interaction. Data are presented as median (range) Thumbnail image of

Gastric emptying

Gastric emptying was significantly delayed in people with diabetes receiving 30 or 60 μg pramlintide. Figure 1 shows the significant overall effect of pramlintide on the estimated t50% values (P < 0.01) relative to placebo. A dose-dependent effect of pramlintide could not be demonstrated (Fig. 2) in either group of participants with diabetes. The magnitude of the delay in gastric emptying was not different in types 1 and 2 diabetics (Fig. 2).

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Figure 1.  Effect of pramlintide on gastric emptying in people with diabetes mellitus (n=12, mean ± SEM). Pramlintide significantly retards gastric emptying t1/2; no dose-related differences were observed.

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Figure 2.  Dose-related effects of pramlintide on gastric emptying in people with type 1 or type 2 diabetes mellitus (n=6 per group, mean ± SEM). The effect of pramlintide did not differ in people with type 1 and type 2 diabetes.

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Plasma pancreatic polypeptide responses

No significant differences in basal pancreatic polypeptide (Fig. 3) concentrations were detected among subjects receiving placebo vs. pramlintide. With pramlintide treatment, postprandial pancreatic polypeptide (Fig. 3) concentrations (P < 0.01) were lower in the entire group of participants with diabetes compared to levels with placebo treatment. Figure 4 shows plots of mean (± SEM) plasma pancreatic polypeptide levels at each timepoint of measurement; after the meal, plasma levels did not differ significantly among pramlintide dosage groups nor between subjects with type 1 or type 2 diabetes.

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Figure 3.  Dose-related effect of pramlintide on fasting and mean (15–90 min) postprandial plasma pancreatic polypeptide level in people with type 1 diabetes mellitus or type 2 diabetes mellitus (n=6 per group, mean ± SEM). The effect of pramlintide did not differ in people with type 1 and type 2 diabetes at the two doses tested.

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Figure 4.  Plots of mean and SEM pancreatic polypeptide at each time point measured in people with type 1 (upper panel) and type 2 (lower panel) diabetes mellitus. Note a reduction in postprandial increase in pancreatic polypeptide in both type 1 and type 2 diabetes mellitus. Though there are trends for greater reduction in type 1 diabetes, there were no significant differences in pancreatic polypeptide levels in the two groups of diabetic subjects in response to the two doses of pramlintide.

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Relationship of gastric emptying and postprandial pancreatic polypeptide response

Figure 5 shows a scatter plot for all data for gastric emptying (t50%) and the postprandial (15–90 min) mean pancreatic polypeptide concentration during treatment with placebo, 30 μg, or 60 μg pramlintide t.i.d. The Spearman rank correlation (r=– 0.66, P < 0.001) was significant.

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Figure 5.  Scatter plot of the gastric emptying t50% and mean (15–90 min) postprandial plasma pancreatic polypeptide levels under treatment with placebo, or 30 μg or 60 μg t.i.d. pramlintide.

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DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES

The novel findings of the present study are firstly, that pramlintide delayed gastric emptying approximately equally in people with type 1 and type 2 diabetes who did not have documented complications (retinopathy, nephropathy, or neuropathy) of diabetes. It is, however, conceivable that an occult neuropathy may have influenced the observations, and future study of patients with formal documentation of peripheral and autonomic nerve function, as well as studies of patients with impaired gastric motor functions are required to fully appraise the effects of pramlintide. Posthoc analysis shows that to detect a clinically significant difference in the response of type 1 and type 2 diabetics to pramlintide (e.g. delta t1/2 of 50 min) would require a sample size of 108 patients; this argues against a true difference in the biological effects of pramlintide in patients with uncomplicated type 1 or type 2 diabetes. A curious finding in our study is that pramlintide appears to have a bigger effect when given in the third period of the crossover design than when given in the first. We do not have an explanation for this finding; there may have been habituation to the experiments, suggesting that an interaction with anxiety may influence the findings. The observed period by dose interaction is complicated by the slight imbalance in the drug-by-period numbers of participants with type 1 vs. type 2 diabetes.

A second finding is that pramlintide attenuates the plasma pancreatic polypeptide response to a meal to a similar extent in both groups of people with diabetes. The early pancreatic polypeptide response to the meal is under cholinergic29 and vagal control.30,31 The reductions in the 15–90 minute postprandial pancreatic polypeptide concentrations and the increase in the gastric emptying t50% are consistent with the hypothesis of inhibition of efferent vagal function by pramlintide. Plasma pancreatic polypeptide response to the meal appears to be different following pramlintide treatment in type 1 and type 2 diabetics, although owing to the small numbers, this was not significant.

Figure 4 also demonstrates that the inhibition of pancreatic polypeptide is evident within the first 15 min post-prandially, when the cephalic phase of the response to a meal is expected.28,29 An alternative explanation is that vagal inhibition delays gastric emptying and that the pancreatic polypeptide response was secondarily diminished by the reduced `enteral' stimulation of pancreatic polypeptide release. This explanation appears less likely to be correct because vagal inhibition accelerates the initial emptying of nutrients in the liquid phase and the test meal included 90–170 kcal in the liquid phase (cream cheese is rapidly liquified at body temperature). Hence, it is reasonable to assume that nutrients reached the duodenum in the early postprandial period, yet the pancreatic polypeptide response was blunted. The data are most consistent with an effect of pramlintide on the cephalic–vagal phase of pancreatic polypeptide release, although such studies in vivo cannot unequivocally prove that the vagus nerve was inhibited.

A third finding was the lack of a dose-related effect of pramlintide on gastric emptying delay in either type 1 or type 2 diabetes. The absence of a dose-related effect of pramlintide was also observed in healthy controls.34 A posthoc analysis shows that to detect a 50-min difference in the gastric emptying t50% between doses would require a sample size of 76 patients, suggesting that the lack of a difference in effects of the two doses tested in the present study is unlikely to be due only to the small sample size. We cannot, however, exclude the possibility that a broader dose range would demonstrate a dose-related effect. Although we did not measure plasma amylin levels in these patients, the literature suggests that the type 1 patients were amylin-deficient and the type 2 patients (who did not require insulin treatment) were unlikely to be amylin-deficient.2–4 Hence, we hypothesize that the endogenous amylin concentrations do not influence the response to 30 and 60 μg t.i.d. pramlintide.

The results of this study also confirm that in people with diabetes, the effect of pramlintide on gastric emptying is significant after 4 days of treatment not only after acute administration as shown in a previous study in the literature.8

The mechanisms of pramlintide-induced delay of gastric emptying are unclear. Possible mechanisms include a direct effect on the stomach by gastrointestinal hormones or an effect on the central nervous system. As no amylin receptors have been identified in the stomach, a direct effect of amylin on the stomach seems unlikely; however, amylin is known to modulate the functions of other hormones. Thus, pramlintide may exert its action on gastric emptying by adding to the inhibition of gastric emptying by endogenously released CCK and the incretins, GLP-1 and GIP.36

The action of pramlintide may also occur via an effect on central control of gastric emptying. Studies in rat brain have revealed the presence of amylin receptors in several regions of the brain, including the area postrema, which is one of the regions that regulate the efferent activity of the vagus nerves.37,38 Further evidence for a vagally mediated action of pramlintide was provided by evidence that subdiaphragmatic vagotomy in rats abolishes the effect of amylin on gastric emptying.9 In dogs,30,31 vagotomy markedly reduces the postprandial pancreatic polypeptide response. In the present study in humans, the plasma pancreatic polypeptide response to a meal observed during the pramlintide-induced delay in gastric emptying and the significant inverse relationship (rank correlation) between these parameters suggest an association between them. Alternatively, pramlintide may affect pancreatic polypeptide response and gastric emptying independently, rather than through a common mechanism such as vagal inhibition. The postprandial increases in the levels of pancreatic polypeptide with 30 and 60 μg pramlintide were significantly lower than those reported for the placebo group in this study, and were also lower than the > 100 pg mL−1 mean pancreatic polypeptide increments in the first postprandial hour in two previous studies.27,32 Although we have not tested the effects of pramlintide in vagotomized patients, the data from studies in rats with subdiaphragmatic vagotomy8 suggest that the effects of pramlintide are due to vagal inhibition. However, we cannot exclude other potential mechanisms.

We also considered the possibility that pramlintide might directly inhibit pancreatic islet cells and the postprandial release of pancreatic polypeptide. While inhibition of insulin secretion in vitro has been observed during augmentation of glucose in physiological doses, high concentrations of amylin (750 pmol L−1) did not inhibit insulin response to more significant hyperglycaemia.39 Because in our previous study in healthy participants, there was no significant change in postprandial glucose in response to pramlintide,34 there appears to be no pramlintide-induced inhibition of insulin secretion. There are no reports in the literature suggesting that amylin directly inhibits pancreatic polypeptide release. However, recent evidence suggests amylin may enhance pancreatic islet cell apoptosis5in vitro. It remains to be seen whether this effect occurs in vivo and what is its timecourse of action.

In summary, 30 μg and 60 μg pramlintide results in an equivalent delay in gastric emptying in people with either type 1 or type 2 diabetes. The delay in gastric emptying in both groups was associated with the pramlintide-induced counteraction of the normal stimulation of postprandial pancreatic polypeptide concentrations. One possible explanation of our findings is that pramlintide delays gastric emptying, at least in part, by inhibition of vagal function. Further studies will be required to determine whether the effects of pramlintide on gastric function in type 1 and type 2 diabetic subjects change over time and whether pramlintide inhibition of gastric emptying is tolerated by people with diabetes mellitus with gastroparesis or patients with asymptomatic but impaired gastric motility. Horowitz et al. suggest that up to 50% of diabetics attending a university clinic have delayed gastric emptying and many do not have symptoms of gastroparesis or a poor prognosis.40 These studies are indicated to ensure that patients with such disorders are not harmed in an attempt to optimize glycaemic control.

ACKNOWLEDGMENTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES

This study was supported in part by Meretek Diagnostics, Inc. (assays for 13CO2 in breath) and by grants from the National Institutes of Health: General Clinical Research Center grant no. RR00585 (Physiology and Immunochemical Core Laboratories), R01-DK54681 (MC), K24-DK02683 (MC), R01-DK29953 (RAR). Study medication was provided by Amylin Pharmaceuticals, Inc., 9373 Towne Centre Drive, San Diego, CA 92121, USA. We thank Mrs Cindy Stanislav for typing and preparing this manuscript.

Footnotes
  1. Potential conflict of interest

  2. Dr Peter D. Klein, who died shortly after completion of this study, was an employee of Meretek Diagnostics, Inc. Two US patents have been awarded to Meretek Diagnostics, Inc. (nos 5707 602 and 5785 949) covering the use of 13C-spirulina (S. platensis) in solid and liquid phase gastric emptying measurements. Dr Rizza has been a consultant for and has received a research grant from Amylin Pharmaceuticals.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES
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