Healthy volunteers were recruited from the Old Order Amish population in Lancaster County, Pennsylvania. After providing informed consent, research participants were screened for eligibility. The clinical trial was designed as a randomized crossover study in which participants underwent two frequently sampled intravenous glucose tolerance tests - one after receiving a subcutaneous injection of saline and one after receiving a subcutaneous injection of rapid-acting exenatide (BYETTA). The study sought to determine whether genetic variants are associated with the magnitude of the effect of exenatide. However, because the study fell far short of its recruitment targets, it was under-powered to evaluate genetic association. Thus, the data analysis focused on testing the hypothesis that the order of testing (whether the placebo FSIGT was conducted before the exenatide-stimulated FSIGT or whether the FSIGTs were conducted in the reverse order) does not alter the magnitude impact of exenatide on responses to a frequently sampled iv glucose tolerance test.
Healthy volunteers were recruited from the Old Order Amish population in Lancaster County, Pennsylvania. After providing informed consent, research participants were screened for eligibility. The clinical trial was designed as a randomized crossover study in which participants underwent two frequently sampled intravenous glucose tolerance tests (FSIGT) - one after receiving a subcutaneous injection of saline and one after receiving a subcutaneous injection of rapid-acting exenatide (BYETTA). Based on data obtained from the FSIGT, participants' response to exenatide was assessed -- specifically, the effect of exenatide to enhance insulin secretion and accelerate metabolism of glucose. The study sought to determine whether genetic variants are associated with the magnitude of the effect of exenatide. However, because the study fell far short of its recruitment targets, it was under-powered to evaluate genetic association. Thus, the data analysis focused on testing the hypothesis that the order of testing (whether the placebo FSIGT was conducted before the exenatide-stimulated FSIGT or whether the FSIGTs were conducted in the reverse order) does not alter the magnitude impact of exenatide on responses to a frequently sampled iv glucose tolerance test.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
Enrollment
63
Nurses administered exenatide (5 mcg) subcutaneously 15 minutes prior to conducting the first frequently sampled intravenous glucose tolerance test. In this crossover study, participants will also be "crossed over" to receive saline rather than exenatide: Nurses administered saline (0.2 mL) subcutaneously 15 minutes prior to conducting a frequently sampled intravenous glucose tolerance test.
Nurses administered exenatide (5 mcg) subcutaneously 15 minutes prior to conducting the second frequently sampled intravenous glucose tolerance test.
Amish Research Clinic
Lancaster, Pennsylvania, United States
Exenatide Effect on First Phase Insulin Secretion
The ratio of the area-under-the-curve (AUC) for 1st phase insulin secretion in the exenatide-stimulated FSIGT divided by the AUC for 1st phase insulin secretion in the saline FSIGT.
Time frame: 0-10 minutes
Exenatide Effect on Glucose Disappearance Rate
The ratio of the glucose disappearance rate (exenatide) divided by the glucose disappearance rate (placebo). Glucose disappearance rates were calculated as the slope of the plot of the logarithm of the glucose concentration as a function of time.
Time frame: 25-50 minutes
Glucose Disappearance Rate (Exenatide)
The slope of the line plotting the logarithm of glucose concentrations as a function of time during the exenatide frequently sampled intravenous glucose tolerance test. The slope of the line was estimated as the slope of the least-squares fit to the data points between 25-50 minutes.
Time frame: 25-50 minutes
Glucose Disappearance Rate (Placebo)
The slope of the line plotting the logarithm of glucose concentrations as a function of time during the placebo frequently sampled intravenous glucose tolerance test. The slope of the line was estimated as the slope of the least-squares fit to the data points between 25-50 minutes.
Time frame: 25-50 minutes
First Phase Insulin Secretion (Exenatide)
The area under the curve for plasma insulin levels during a frequently sampled intravenous glucose tolerance test after participants received exenatide
Time frame: 0-10 minutes
First Phase Insulin Secretion (Placebo)
The area under the curve for plasma insulin levels during a frequently sampled intravenous glucose tolerance test after participants received saline
Time frame: 0-10 minutes
Drug Effect on First-Phase Insulin Secretion (Genotype-specific)
The effect of exenatide to increase first-phase insulin secretion was defined as the ratio of area-under-the-curve (AUC) for insulin levels during the first 10 minutes of the exenatide-stimulated FSIGT divided by the AUC for first phase insulin secretion during the saline FSIGT..
Time frame: 0 - 10 min during the FSIGT
Exenatide's Effect on the Rate of Glucose-disappearance (Genotype Specific)
The rate of glucose disappearance was calculated as the slope of a least-squared line fitted to the logarithms of glucose concentrations during time 25-50 min of FSIGTs
Time frame: 25-50 min during the FSIGT
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