Interaction of Melatonin and MTNR1B Genotype on Glucose Control - Study 1

The investigators' recent GWAS discovery of MTNR1B as a novel type 2 diabetes gene has
sparked great interest into the role of melatonin in glycemic control, for which the
mechanism is largely unknown. This research will determine the effect of melatonin and MTNR1B
on glycemic control under highly-controlled, in-laboratory protocols while manipulating
circulating melatonin concentrations (both up and down) and assessing glycemic control by
frequently-sampled intravenous glucose tolerance tests, as well as in ex vivo human
pancreatic islets. This research will provide mechanistic insights into the metabolic effects
of melatonin and the MTNR1B risk variant and may help in evidence-based approaches and
personalized recommendations to improve glycemic control in night shift workers and
late-night eaters.

Inclusion Criteria:

- Body Mass Index: 20 and 35 kg/m2

- Age: 21-55 years of age

- Caucasian

- Non-smoking

- With regular sleep-wake cycle

- Passed medical and psychological screening tests

Exclusion Criteria:

- Acute, chronic or debilitating medical conditions

- History of neurological or psychiatric disorder

- History of sleep disorder or regular use of sleep-promoting medication

- Current prescription, herbal, or over-the-counter medication use

- Traveling across 2 or more time zones within past 3 months

- Worked night or rotating shift work within past 1 year

- Drug or alcohol dependency