Almond Effects on Glucose Intolerance Study
| Status: | Enrolling by invitation |
|---|---|
| Conditions: | Endocrine |
| Therapuetic Areas: | Endocrinology |
| Healthy: | No |
| Age Range: | 18 - 75 |
| Updated: | 4/21/2016 |
| Start Date: | December 2014 |
| End Date: | March 2016 |
Almond Effects on Glucose Intolerance Study (AEGIS)
Diabetes is a major cause of morbidity and mortality worldwide. Prevention of diabetes is an
important goal. The progression from impaired glucose tolerance to diabetes is thought to be
promoted by the toxic effects of hyperglycemia on pancreatic beta cells. One of the main
defects causing postprandial hyperglycemia in individuals with impaired glucose tolerance is
reduced first phase (immediate) insulin release. The investigators hypothesis is that
consuming a nutritional preload--a low-calorie, nutritionally balanced snack--30 minutes
before ingesting a carbohydrate load, will moderate the hyperglycemic response to subsequent
carbohydrate challenge and reduce glucotoxicity by stimulating insulin release and
synthesis.
The aim of this study is to test this hypothesis by comparing the standard 75-gram, two-hour
oral glucose tolerance test (OGTT) response of 30 fasting adults who have impaired glucose
tolerance to their OGTT response when the test is preceded by ½ ounce (14 grams) of
dry-roasted, unsalted almonds. A pre-load interval of 30 minutes was chosen so that the peak
of phase 2 (delayed) insulin response to the pre-load (45-60 minutes) would coincide with
the timeframe of the steepest OGTT rise in glucose (15 to 30 minutes post challenge).
The investigators hypothesize that the one-hour OGTT glucose level will be approximately 40
mg/dl lower when participants consume the pre-OGTT almond snack, compared to their one-hour
glucose level on the standard two-hour OGTT. The two-hour OGTT glucose level is unlikely to
show a statistically significant difference between the almond pre-test snack and control
standard OGTT conditions.
important goal. The progression from impaired glucose tolerance to diabetes is thought to be
promoted by the toxic effects of hyperglycemia on pancreatic beta cells. One of the main
defects causing postprandial hyperglycemia in individuals with impaired glucose tolerance is
reduced first phase (immediate) insulin release. The investigators hypothesis is that
consuming a nutritional preload--a low-calorie, nutritionally balanced snack--30 minutes
before ingesting a carbohydrate load, will moderate the hyperglycemic response to subsequent
carbohydrate challenge and reduce glucotoxicity by stimulating insulin release and
synthesis.
The aim of this study is to test this hypothesis by comparing the standard 75-gram, two-hour
oral glucose tolerance test (OGTT) response of 30 fasting adults who have impaired glucose
tolerance to their OGTT response when the test is preceded by ½ ounce (14 grams) of
dry-roasted, unsalted almonds. A pre-load interval of 30 minutes was chosen so that the peak
of phase 2 (delayed) insulin response to the pre-load (45-60 minutes) would coincide with
the timeframe of the steepest OGTT rise in glucose (15 to 30 minutes post challenge).
The investigators hypothesize that the one-hour OGTT glucose level will be approximately 40
mg/dl lower when participants consume the pre-OGTT almond snack, compared to their one-hour
glucose level on the standard two-hour OGTT. The two-hour OGTT glucose level is unlikely to
show a statistically significant difference between the almond pre-test snack and control
standard OGTT conditions.
The study will be conducted at Physicians at Sugar Creek (PSC)—the model family practice
center for the Memorial Family Medicine Residency Program. The ethnicity of PSC patients is
approximately 30% non-Hispanic white, 30% Hispanic, 30% African-American, and 10% Asian.
Potential participants will be identified by searching PSC electronic medical records
(Centricity) to find adults aged 18-75 with impaired glucose tolerance, without diabetes
(one-hour oral glucose tolerance test result >160 md/dl and two-hour OGTT result <200
mg/dl), without hypoglycemic medications and corticosteroids on their active medications
list, and without almond allergy on their allergy list.
Recruitment flyers will be posted in the clinic to encourage interested individuals to
contact the investigators about their potential study eligibility. The investigators will
also approach previously identified potentially eligible patients during routine clinical
visits in the clinic, to elicit their interest in participating in the study. Those
expressing interest will be scheduled for an intake visit with an investigator, to further
ascertain their eligibility and invite eligible individuals to take part in the study.
Interested eligible individuals who render verbal and written informed consent will then be
instructed in the study protocol and scheduled for their first data gathering visit.
Each participant will be scheduled to undergo two 2-hour oral glucose tolerance tests
(OGTT), starting between 7:00 and 9:30 a.m., one to four weeks apart. Test A will be a
standard 75-gram OGTT. Test B will be an OGTT that will begin 30 minutes after ingestion of
a low-carbohydrate pre-load "snack" consisting of 1/2 oz (14 grams) of unsalted, dry-roasted
almonds (12 average size almonds). Each participant will be given an 8-ounce glass of water
to drink with the almonds. Participants will be randomized to one of two test sequences (A-B
or B-A), to control for sequence effects on results.
To minimize variability of OGTT results, participants will be asked to eat as they usually
do throughout the study. Participants will be asked to refrain from vigorous physical
activity for 8 hours prior to each OGTT and to minimize their physical activity during each
OGTT. Participants will complete a Perceived Stress Scale and a 24-hour food, alcohol, and
activity recall for the day before each OGTT to analyze potential confounding effects of
stress, diet, alcohol, and physical activity on the results.
Blood sampling will be done for serial measurements of plasma glucose at time-zero, and at
60-minute intervals for two hours after each 75-gram glucose load. An investigator will
monitor the timing of each blood draw closely to ensure timeliness. Blood will be drawn by
one of two phlebotomists in the on-site laboratory and sent to the Memorial Hermann
Southwest Hospital or Quest Lab (the latter only for the control OGTT, for patients whose
insurance requires this) for analysis. The glucose results will be reported electronically
to the patient's medical record in the routine manner for blood test results.
Investigators will abstract the glucose results from the patients' electronic medical
records for data analysis purposes. The primary dependent variable is the mean difference in
plasma glucose (fasting to 1-hr post 75-g glucose challenge, with vs. without snack. The
secondary dependent variable is the mean difference in plasma glucose (fasting to 2-hr post
75-g glucose challenge, with vs. without snack). Student's t test will be used to analyze
the differences between the standard 75-g OGTT results and the OGTT results following the
almond pre-test snack. Analysis of variance will be used to analyze the data for confounding
effects of ethnicity, gender, body mass index (BMI), and pre-test food and alcohol intake,
physical activity, and perceived stress level.
Patients will receive their individual results and an investigator-generated evaluative
commentary in a routine "lab letter". The results letter will be forwarded to each patient's
primary care provider for review and appropriate clinical follow-up. Patients' results will
be communicated scientifically in an aggregate manner, with no individual identifying
information, to maintain patient confidentiality.
center for the Memorial Family Medicine Residency Program. The ethnicity of PSC patients is
approximately 30% non-Hispanic white, 30% Hispanic, 30% African-American, and 10% Asian.
Potential participants will be identified by searching PSC electronic medical records
(Centricity) to find adults aged 18-75 with impaired glucose tolerance, without diabetes
(one-hour oral glucose tolerance test result >160 md/dl and two-hour OGTT result <200
mg/dl), without hypoglycemic medications and corticosteroids on their active medications
list, and without almond allergy on their allergy list.
Recruitment flyers will be posted in the clinic to encourage interested individuals to
contact the investigators about their potential study eligibility. The investigators will
also approach previously identified potentially eligible patients during routine clinical
visits in the clinic, to elicit their interest in participating in the study. Those
expressing interest will be scheduled for an intake visit with an investigator, to further
ascertain their eligibility and invite eligible individuals to take part in the study.
Interested eligible individuals who render verbal and written informed consent will then be
instructed in the study protocol and scheduled for their first data gathering visit.
Each participant will be scheduled to undergo two 2-hour oral glucose tolerance tests
(OGTT), starting between 7:00 and 9:30 a.m., one to four weeks apart. Test A will be a
standard 75-gram OGTT. Test B will be an OGTT that will begin 30 minutes after ingestion of
a low-carbohydrate pre-load "snack" consisting of 1/2 oz (14 grams) of unsalted, dry-roasted
almonds (12 average size almonds). Each participant will be given an 8-ounce glass of water
to drink with the almonds. Participants will be randomized to one of two test sequences (A-B
or B-A), to control for sequence effects on results.
To minimize variability of OGTT results, participants will be asked to eat as they usually
do throughout the study. Participants will be asked to refrain from vigorous physical
activity for 8 hours prior to each OGTT and to minimize their physical activity during each
OGTT. Participants will complete a Perceived Stress Scale and a 24-hour food, alcohol, and
activity recall for the day before each OGTT to analyze potential confounding effects of
stress, diet, alcohol, and physical activity on the results.
Blood sampling will be done for serial measurements of plasma glucose at time-zero, and at
60-minute intervals for two hours after each 75-gram glucose load. An investigator will
monitor the timing of each blood draw closely to ensure timeliness. Blood will be drawn by
one of two phlebotomists in the on-site laboratory and sent to the Memorial Hermann
Southwest Hospital or Quest Lab (the latter only for the control OGTT, for patients whose
insurance requires this) for analysis. The glucose results will be reported electronically
to the patient's medical record in the routine manner for blood test results.
Investigators will abstract the glucose results from the patients' electronic medical
records for data analysis purposes. The primary dependent variable is the mean difference in
plasma glucose (fasting to 1-hr post 75-g glucose challenge, with vs. without snack. The
secondary dependent variable is the mean difference in plasma glucose (fasting to 2-hr post
75-g glucose challenge, with vs. without snack). Student's t test will be used to analyze
the differences between the standard 75-g OGTT results and the OGTT results following the
almond pre-test snack. Analysis of variance will be used to analyze the data for confounding
effects of ethnicity, gender, body mass index (BMI), and pre-test food and alcohol intake,
physical activity, and perceived stress level.
Patients will receive their individual results and an investigator-generated evaluative
commentary in a routine "lab letter". The results letter will be forwarded to each patient's
primary care provider for review and appropriate clinical follow-up. Patients' results will
be communicated scientifically in an aggregate manner, with no individual identifying
information, to maintain patient confidentiality.
Inclusion Criteria:
- History of abnormal 1-hour OGTT result (>160 mg/dL) or 2-hour OGTT (>140)
Exclusion Criteria:
- History of a diagnosis of diabetes
- History of a 2-hour OGTT result >200 mg/dL
- History of a fasting glucose >125 mg/dL
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