Glucose Intolerance
Conditions
Brief summary
Specific aims of the study are: 1. to evaluate whether a 24-h exposure to a 25%-carbohydrate diet will reduce postprandial glycemia to the same extent in the evening (19 h) as in the morning (7 h),. and 2. to determine whether one hour of post-meal moderate intensity exercise (at 50% of maximal effort) will further reduce postprandial glycemia. The outcome measures are: plasma concentrations of glucose, insulin, glucose-dependent-insulinotropic peptide (GIP), leptin, and the ketone body beta-hydroxybutyrate.
Detailed description
The two hypotheses in this study are: 1. A 24-h exposure to a 25%-carbohydrate diet will reduce postprandial glycemia to the same extent in the evening (19 h) as in the morning (7 h), and 2. One hour of moderate-intensity exercise (at 50% of maximal effort) will further reduce postprandial glycemia to the same extent in the evening (19 h) as in the morning (7 h). Eight postmenopausal subjects (age 58.5 years, BMI 25.6 kg/m2) participated in 4 24-h long crossover trials, two terminating at 7h and the other 2 at 19h. At each circadian time one trial required 60 minutes of moderate-intensity exercise (50% of maximal effort), and the other two involved no exercise. Three 25%-carbohydrate meals prepared by the Michigan Clinical Research Unit (MCRU) kitchen, were eaten at subjects' home, and the fourth was eaten 20 minutes after subjects' arrival at MCRU at either 19 h or 7 h. Blood was collected from antecubital catheter at 10-minute intervals until 23:20 h or 11:20 h, respectively.Plasma was treated with protease inhibitor to preserve GIP, frozen at -80o C until glucose measurements by glucose oxidase, hormone measurements by chemiluminescence, and ketone measurements by Abbott meter strips. Exercise intensity was determined before the exercise trials on a treadmill from oxygen consumption (VO2) and carbon dioxide production (VCO2) by subjects walking on a treadmill at 3 mph with the treadmill slope increased by 2% every 3 minutes. Maximal effort was established when respiratory exchange ratio (VCO2/VO2) reached or exceeded 1. The treadmill speed and slope at half maximal effort was used during the one-hour exercise bout which was initiated 40 minutes after the start of the meal.
Interventions
COMBINATION_PRODUCTDietary manipulation (25% carbohydrate diet) and behavioral (exercise)
The 25% carbohydrate diet consisted of Pulmocare-vanilla liquid, white roll, butter, and string cheese in proportions to achieve 33% of weigh-maintenance diet containing 25% carbohydrate, 20% protein, and 55% fat. Exercise was walking 1 hour on level treadmill at 50% of maximal effort starting 40 minutes after the beginning of the meal
COMBINATION_PRODUCTDietary manipulation (25% carbohydrate diet) and behavioral (sedentary)
The 25% carbohydrate diet consisted of Pulmocare-vanilla liquid, white roll, butter, and string cheese in proportions to achieve 33% of weigh-maintenance diet containing 25% carbohydrate, 20% protein, and 55% fat. There was no exercise during this trial.
Sponsors
Northern Michigan University
University of Michigan
Study design
Allocation
NON_RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
NONE
Intervention model description
The same eight subjects participated in counterbalanced order in: (1) sedentary morning trial, (2) exercise morning trial, (3) sedentary evening trial, (4) exercise evening trial.
Eligibility
Sex/Gender
FEMALE
Age
50 Years to 65 Years
Healthy volunteers
Yes
Inclusion criteria
* postmenopausal * normal blood glucose * no cholesterol medication * age between 50 an 65 years * overweight but not obese * BMI between 25 and 30 kg/m2 * weight-stable during past 6 months * exercise less than 20 minutes three times a week
Exclusion criteria
* metabolic disease other than hormonally-corrected hypothyroidism * musculo-skeletal disability that would preclude exercise * smoker * do not meet inclusion criteria
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Postprandial glucose concentration | Four hours: 19:20 to 23:20 in the evening trials; 7:20 to 11:20 in the morning trials | The area under the postprandial glucose curve |
| Postprandial insulin concentration | Four hours: 19:20 to 23:20 in the evening trials; 7:20 to 11:20 in the morning trials | The area under the postprandial insulin curve |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Postprandial glucose-dependent insulinotropic peptide (GIP) concentration | Four hours: 19:20 to 23:20 in the evening trials; 7:20 to 11:20 in the morning trials | The area under the postprandial GIP curve |
| Postprandial beta-hydroxybutyrate concentration | Four hours: 19:20 to 23:20 in the evening trials; 7:20 to 11:20 in the morning trials | The area under the beta-hydroxybutyrate postprandial curve |
| Postprandial leptin concentration | Four hours: 19:20 to 23:20 in the evening trials; 7:20 to 11:20 in the morning trials | The area under the leptin postprandial curve |
Outcome results
None listed