Effect of Sleep Restriction on Adipose Tissue and Skeletal Muscle Insulin Sensitivity

Inadequate sleep is an independent risk factor for metabolic abnormalities (such as obesity, insulin resistance, and hyperglycemia). Women report sleep disruption during the menopause transition (perimenopause) and into the postmenopausal years. Sleep disruption is one of the primary reasons why midlife women seek medical care, with up to 60% reporting significant sleep disturbances (e.g., trouble falling asleep, early morning waking, and hot flashes/night sweats). Despite the majority of women experiencing sleep disruption, no study has investigated the molecular mechanisms linking sleep disruption and the changes in metabolism that coincide with menopause.

The investigators will conduct a randomized, crossover trial investigating the effect of sleep restriction compared to habitual sleep on adipose tissue and skeletal muscle insulin sensitivity in vivo and ex vivo. The investigators will randomize up to 10 healthy postmenopausal women with overweight/obesity and ≥6.5 hours of self-reported habitual nightly sleep to 4 nights of each sleep condition (sleep restriction and habitual sleep). After the fourth night of each sleep condition, the investigators will administer a two-step hyperinsulinemic-euglycemic clamp and collect skeletal muscle and adipose tissue samples prior to insulin infusion.

The overarching hypothesis is that sleep restriction will reduce skeletal muscle and adipose tissue insulin sensitivity compared to habitual sleep.

Eligibility Criteria:
INCLUSION CRITERIA:

* Body mass index (BMI) 25-35 kg/m2 (inclusive)
* Postmenopausal (self-reported absence of menstrual cycle for 1-year)
* Within 10 years of final menstrual cycle
* Self-reported nocturnal time in bed of ≥6.5 hours per night (for ≥5 nights during a usual week)
* Willing to not take naps or engage in moderate-to-vigorous physical activity/exercise during both sleep conditions
* Willing to consume only the meals provided during both sleep conditions
* Willing to have adipose tissue and skeletal muscle biopsies
* Willing to have blood, as well as adipose and muscle tissue stored for future use

EXCLUSION CRITERIA:

* Unstable weight in the last 3 months \[gain or loss ≥5% of body weight\]
* History of clinically diagnosed diabetes or a fasting blood glucose \>126 mg/dL
* History of polycystic ovary syndrome (PCOS)
* Currently taking antihypertension medication known to affect adipose tissue and skeletal muscle metabolism (e.g., diuretics may be allowed)
* Chronic use of systemic glucocorticoids
* Chronic use of atypical antipsychotic or bipolar medications
* Initiation of antidepressant medication within the last 3 months
* Previous bariatric surgery (or other surgeries) for obesity or weight loss
* Chronic use of prescription or 'effective' over-the-counter medications affecting sleep, circadian rhythms, or glucose metabolism †
* Chronic use of hormone replacement therapy
* History of clinically diagnosed sleep apnea
* Shift workers (e.g., individuals awake or working between Midnight and 5AM)
* Inability to spend 5 nights at Pennington Biomedical
* Unwilling to eat only the food and drink provided by study staff while in the study
* Unwilling to maintain a consistent and prescribed sleep schedule while in the study
* Unwilling to maintain a consistent eating schedule while in the study

Sporadic use of certain medications is fine (however, enrollment will depend on a case-by-case basis). If taking sporadically, women should not be taking the medication for 1-month prior to the first Run-In period.