Metabolic effects of morning light in obesity and type 2 diabetes

Type 2 diabetes is a major threat to human health. Interestingly, the incidence
of obesity and type 2 diabetes correlates to the presence of artificial light.
Light for the non-visual system is detected in the retina by specialised
intrinsically photosensitive retinal ganglion cells (ipRGCs) that communicate
directly to various hypothalamic areas, and thereby modulate hormonal secretion
and autonomic activity. Light has time dependent autonomic effects in humans,
and administration of a light pulse to rats directly alters metabolic gene
expression in the liver. In a previously performed pilot study (METC 2012-341)
light intensity did not directly affect the postprandial glucose and insulin
levels in healthy lean males. In this second pilot study, we aim to determine
if light directly influences human glucose metabolism in subjects with
prediabetes (impaired glucose tolerance) and in subjects with type II diabetes.
We hypothesize that morning bright light exposure decreases postprandial
glucose excursions.

To determine the direct effects of morning light intensity on postprandial
glucose and lipid metabolism and metabolic gene expression in adipose tissue in
obese subjects with and without type 2 diabetes.

cross-over intervention study

Subjects enter the facility in the evening. They will remain in normal room
light (100-200 lux) for 4 hours. They receive a standard meal 2 hrs before
bedtime. They sleep for 8 hrs in the dark (1 lux). From wake-up time, they will
be subjected to either bright light (4000 lux) emitted by EnergyLights
((Philips Consumer Lifestyle B.V., Drachten) or dim light (10 lux). 1 hr after
lights on subjects will consume a standard 600 kcal liquid meal (EnsurePlus,
Abbott Industries, 16.7% proteins, 53,8% carbohydrates, 29,5% fat). Blood
samples will be obtained at regular intervals until 5 h after the meal. Resting
energy expenditure (REE) will be measured 3.5 h after breakfast, An adipose
tissue biopsy will be obtained 4 h after the meal. Visual scale questionnaires
will be rated to assess hunger and satiety.

Total study duration is three weeks. Participants will visit the Academic
Medical Center five times: three short visits (<1hr) and two 16h admissions. At
study entry, patients will undergo physical examination and one blood sample
will be obtained. Participants will record sleep-wake times in a diary for five
days. Prior to each admission they will wear an actiwatch to verify adherence
to a stable sleep-wake rhythm. During each admission, participants will sleep
for one night at 1 lux in the experimental room. They will remain undisturbed
during this night. In the morning blood samples will be obtained from an
indwelling canula in a peripheral arm vein. Total amount of blood obtained
during the study will be 210 ml (100 ml at each admission and 10 ml at study
entry). Subcutaneous adipose tissue biopsies from the periumbilical region will
cause minor discomfort and a subcutaneous hematoma that will resolve over
time. Subcutaneous adipose tissue biopsies have negligible risks of infection
or haemorrhage. Use of EnergyLights may cause minor temporal complaints such as
headache or tired eyes. The 400 ml (600 kcal) Ensure Plus breakfast may for
some people be above the average breakfast size. This may cause a transient
sense of fullness.
Patients will receive a financial compensation of 200 euros and travel
expenses.