Effects of Diet and Exercise on Circadian Glycemia

Not Applicable

Completed

• Conditions: Glucose Intolerance
• Interventions: Combination Product: Dietary manipulation (25% carbohydrate diet) and behavioral (sedentary); Combination Product: Dietary manipulation (25% carbohydrate diet) and behavioral (exercise)

• Registration Number: NCT03922685
• Lead Sponsor: University of Michigan

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.

Study Timeline

• Study Start: 2016-09-01
• Primary Completion: 2017-08-31
• Status Verified: 2019-04
• Study Completion: 2019-04
• Study First Submitted: 2019-04-17
• Study First Submitted QC: 2019-04-17
• Last Update Submitted: 2019-04-17
• Study First Posted: 2019-04-22
• Last Update Posted: 2019-04-22

Recruitment & Eligibility

• Status: COMPLETED
• Sex: Female
• Target Recruitment: 8

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

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Exclusion Criteria

• metabolic disease other than hormonally-corrected hypothyroidism
• musculo-skeletal disability that would preclude exercise
• smoker
• do not meet inclusion criteria

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Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Evening sedentary arm	Dietary manipulation (25% carbohydrate diet) and behavioral (sedentary)	After arriving at MCRU at 19 h, and having eaten three 25%-carbohydrate meals over the previous 24 h, subjects had an antecubital-vein catheter inserted and consumed their fourth 25%-carbohydrate meal at 19:20 h. Over the next 4 hours, subjects reclined on a bed and had 3-ml blood samples collected at 10-min intervals. After the 23:20 blood sample, subjects were released from MCRU. This arm is compared to the other three arms.
Morning sedentary arm	Dietary manipulation (25% carbohydrate diet) and behavioral (sedentary)	After arriving at MCRU at 7 h, and having eaten three 25%-carbohydrate meals over the previous 24 h, subjects had an antecubital-vein catheter inserted and consumed their fourth 25%-carbohydrate meal at 7:20 h. Over the next 4 hours, subjects reclined on a bed and had 3-ml blood samples collected at 10-min intervals. After the 11:20 blood sample, subjects were released from MCRU. This arm is compared to the other three arms.
Morning exercise arm	Dietary manipulation (25% carbohydrate diet) and behavioral (exercise)	After arriving at MCRU at 7 h, and having eaten three 25%-carbohydrate meals over the previous 24 h, subjects had an antecubital-vein catheter inserted and consumed their fourth 25%-carbohydrate meal at 7:20 h. At 8 h, subjects walked on the treadmill at 50% maximal effort. Between 7:20 and 11:20, 3-ml blood samples were collected at 10-min intervals.After the 11:20 blood sample, subjects were released from MCRU. This arm is compared to the other three arms.
Evening exercise arm	Dietary manipulation (25% carbohydrate diet) and behavioral (exercise)	After arriving at MCRU at 19 h, and having eaten three 25%-carbohydrate meals over the previous 24 h, subjects had an antecubital-vein catheter inserted and consumed their fourth 25%-carbohydrate meal at 19:20 h. At 8 h, subjects walked on the treadmill at 50% maximal effort. Between 19:20 and 23:20, 3-ml blood samples were collected at 10-min intervals.After the 23:20 blood sample, subjects were released from MCRU. This arm is compared to the other three arms.

Primary Outcome Measures

Name	Time	Method
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 Outcome Measures

Name	Time	Method
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
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