The Effects of Light on Glucose Metabolism

Study Overview
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Brief Summary
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This study evaluates the effect of bright light on postprandial blood glucose metabolism in obese subjects with impaired fasting glucose and/or impaired glucose tolerance.

Detailed Description
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Light has a major influence on the biological clock and several studies suggest that bright light during the day and dim light in the evening are beneficial for the circadian timing system. Nowadays, large parts of the population spend 90% of their time indoors and are thereby exposed to artificial lighting instead of daylight. The artificial light levels are relatively low during the day and continue relatively late in the evening. The lack of a clear natural light-dark cycle could results in delayed timing of the biological clock relative to the behaviour. Optimizing the lighting conditions under controlled laboratory settings might lead to better alignment of the biological clock, which in turn could improve metabolic parameters such as glucose control.

Official Title
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The Effects of Light on Glucose Metabolism

Conditions
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Diabetes Mellitus, Type 2, Glucose Intolerance, Prediabetic State

Intervention / Treatment
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* Behavioral: Exposure to bright light during the day
* Behavioral: Exposure to dim light during the day


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Caucasian BMI 25-35 kg/m2 Stable weight (+/- 3 kg in the last 3 months) One of the four criteria for prediabetes: Impaired fasting glucose (6.1 mM to 6.9 mM) Blood glucose values 7.8 - 11.1 mM 2h after glucose drink consumption during the oral glucose tolerance test (OGTT) in screening Insulin Resistance: glucose clearance rate ≤ 360 ml/kg/min, as determined using the oral glucose insulin sensitivity (OGIS120) index HbA1c of 5.7 - 6.4%. Exclusion Criteria: Fasting plasma glucose ≥7.0 mM Blood donation one month prior to study and three months after finishing study. Participants with extreme chronotypes (going to bed extremely late/early).

Ages Eligible for Study
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Minimum Age: 40 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: bright light during the day<br>Participants will be exposed to bright light (1250 lux) between 8:00 and 18:00 and to dim light (5 lux) between 18:00 and 23:00. | Behavioral: Exposure to bright light during the day<br>* Participants will be exposed to bright light (1250 lux) between 8:00 and 18:00 and to dim light (5 lux) between 18:00 and 23:00.<br>|
| Experimental: dim light during the day<br>Participants will be exposed to dim light (10 lux) between 8:00 and 18:00 and to dim light (1250 lux) between 18:00 and 23:00. | Behavioral: Exposure to dim light during the day<br>* Participants will be exposed to dim light (10 lux) between 8:00 and 18:00 and to dim light (1250 lux) between 18:00 and 23:00.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Postprandial glucose (mg/dL) | Assessed with a continuous glucose monitor (CGM) | Study Day 1-3 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Glucose levels (mmol/L) in the postprandial state | venous blood draw every 30 min for 4 hours after breakfast and after dinner | Study Day 2-3 | 
| Free fatty acid levels (µmol/L) in the postprandial state | venous blood draw every 30 min for 4 hours after breakfast and after dinner | Study Day 2-3 | 
| Triglycerides levels (mmol/L) in the postprandial state | venous blood draw every 30 min for 4 hours after breakfast and after dinner | Study Day 2-3 | 
| Insulin levels (µU/mL) in the postprandial state | venous blood draw every 30 min for 4 hours after breakfast and after dinner | Study Day 2-3 | 
| Continuous interstitial glucose (mg/dL) | Assessed with continuous glucose monitor (CGM) | Study Day 1-3 | 
| Energy expenditure | continuous measurement with whole room indirect calorimetry | Study Day 1-3 | 
| Core body temperature (CBT) and skin temperature | Measured with a telemetric pill (CBT) and 14 temperature sensors (iButtons) in degrees celsius | Study Day 1-3 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Circadian Rhythm